I decided to write down some of the things my older sister Melissa (not her real name) told me about that happened to both her and our mom. It all took place in the San Francisco Bay Area. Some of the paranormal activity happened in a duplex house in Alameda where I grew up, although strangely enough, nothing happened while I was living there, so I didn't get to experience any of this first-hand. I moved out in 1992, and our brother moved out in 1995, leaving just Melissa and our mom living there.
Adjacent to the living room was my old bedroom, which also served the dual purpose as a storage room where the types of things that a family normally stores were kept on shelves, and stacked in boxes on the floor. On a couple of different occasions, Melissa and our mom would be sitting watching TV in the living room, and suddenly they would both be startled by a crashing-tumbling sound inside the storage room as though a bunch of stuff had just fallen over and was breaking and shattering. They would go into the room to check it out, expecting to see a mess, but absolutely nothing would be out of place. On one occasion that same crashing sound was coming from the kitchen, and again nothing was out of place.
One morning our mom was in the bathroom getting ready for her day. From the vantage point of looking into the bathroom mirror, the reflection gave her a view of the hallway just outside the open bathroom door. As she was fixing her hair in the mirror, she saw someone walk past the bathroom doorway in the hall. She was the only one home at that time. When she later relayed this incident to me, she said that the 'person' looked like me! She remembered saying to herself, "What's Dave doing here?" By that time, I was living clear on the other side of the San Francisco Bay. It certainly wasn't me, but it was a male with the same build and general appearance (you can see my self portrait in my profile page).
There were nights when the entity that was haunting the duplex would crawl into bed with Melissa, and on alternate nights it would crawl into bed with our mom. They both told me that their bedding would rustle like someone was slipping under the covers, followed by the sensation of someone breathing on their necks.
Melissa and our mom moved out of the Alameda duplex in the year 2001, and into a two-bedroom, double-wide trailer within a trailer park in San Leandro. It's interesting to note that the Alameda duplex is still vacant to this day. After almost 12 years, the landlord has been unable to keep a tenant in it for very long, due to the paranormal activity. This information was provided to me by the neighbor across the street from the duplex who has been a family friend for decades.
Once Melissa and our mom moved into the trailer, it wasn't long before lots of paranormal stuff started happening there too.
Our mom spent a lot of time baby sitting her grandson (my brother's son). There were some toys that he played with while he was being babysat. Those toys were kept in the corner of the living room, and they always remained at our mom's house, even after my brother picked his up son in the evening, so that the toys would conveniently be there next time my brother brought his son over. Melissa said that in the middle of the night she would be awoken hearing some of the toys turning on by themselves. Sometimes it was the talking Elmo doll uttering one of its programmed phrases, or it would be one of the choo-choo train engines making different train noises.
One evening when Melissa was sitting in the living room with the cat on her lap watching TV, she felt a cold 'breeze' come straight out of the wood paneling of the wall next to her easy chair, and waft past her. On Melissa's lap, the cat's pupils dilated, because it was able to sense this invisible thing, and the kitty's head quickly turned, tracking the entity as it drifted across the living room toward the corner where the toys were kept, and right then the Elmo doll started talking. In fact it became almost a routine for the cat to see something invisible emerging from that same spot on the wall, and shooting across the living room, but the toys wouldn't always turn on afterward. It may be worth mentioning that directly on the other side of that wall was Melissa's bedroom closet, and that while she was lying in bed, she would sometimes hear shuffling noises inside that closet, even though the cat was also lying on the bed, so the shuffling couldn't have been the cat.
Melissa's bedroom had its own adjoining bathroom. When she was in the shower, the toilet would sometimes flush by itself. Also, I remember her telling me that she would straighten the towel that was hanging on the bathroom's towel rack, and every time she came back into the bathroom the corner of the towel was flipped up. No matter how many times she flipped the towel's corner back down, and carefully re-straightened the towel, it would be flipped up next time she came back into the bathroom.
Our mom was changing her grandson's diaper one day in her bedroom, and while the grandson was lying there looking up at the ceiling, he smiled saying, "Hi grandma! What are you doing up there?" Apparently he was seeing 'someone' floating just below the ceiling that bore a resemblance to our mom, namely an older woman with white hair looking down at him, and mistook it for his grandma.
One night Melissa was lying in bed right after having turned off the bedroom light, and then directly into her ear an old woman's voice called her name, sharply, "Melissa!"
Melissa recalled a moment when she was looking out the window of the kitchen while doing dishes, and she saw a really pale old man in a red plaid shirt standing just outside in the driveway. She didn't have time to wonder who it was, because by then he disappeared into thin air.
In 2005, our mom got cancer, and one morning she died in her bed in that trailer, and so that day her body was taken to a funeral parlor for embalming. That night as Melissa was lying in bed, she clearly heard our mom's voice whispering in her ear, "Melissa, I'm still here!"
That trailer park in San Leandro is almost entirely populated with elderly people, so I imagine that a good proportion of them die there in their trailers. It would be interesting to find out how many of the trailers are haunted.
Looking back, I believe that the activity originally started in the Alameda duplex because Melissa had a fondness for the Ouija board, and also for experimenting with automatic writing (psychography). One could easily find other submissions on this web site demonstrating that engaging in such practices is likely to open a 'portal' that will let negative entities come through. It's my understanding that any time you invite, or give permission for an entity to come into your space, you're asking for trouble. Once our mom died, and Melissa was alone and lonely, she ended up having conversations with three entities via automatic writing, but eventually she began to be able to see and hear them, and have conversations with them by simply talking back and forth without using any writing.
Things went seriously downhill from there, because these entities started telling her what to do, and what not to do. She started acting irrationally and impulsively. She went AWOL (absent without leave) from her job, and so they fired her. She then squandered all of her savings, and couldn't pay her rent, so she got evicted from her rental apartment, and all her belongings were auctioned off (family heirlooms too). She is now homeless, and penniless. I have no idea where she is, or if she's still alive. The last thing I heard was from other relatives in the Bay Area whom she paid a visit to, asking them if she could crash at their place, but everyone told her that she wasn't acting like the real Melissa anymore, and that she should go to the homeless shelter. My brother and I are both in no position to be able to help her either. Sorry for such an ending, but that's exactly how it all turned out. From a medical standpoint, one might say that Melissa has schizophrenia, but who can say that this isn't an example of how dangerous it can be for someone with a weak mind to blindly, and recklessly try to make contact with the spirit world?
As for your sister it sounds like she lost her grip with reality. I assume she is the one who found your mother. She may have had some sort of breakdown afterwards or a total psychotic episode. You or your brother can become her custodian and have her committed.
The paranormal events that happened to your sister and mother might have started with the Ouija Board and if they brought it to the trailer with them something attached to it may have followed.
I hope she gets the help she needs because having conversations with people who aren't there may have nothing to do with the paranormal. To rule this out you may want to find a psychic/medium who can either deny or confirm the belief that something is controlling her.