I don't know if you will find this experience interesting as it wasn't really in retrospect very dramatic but it is by far the freakiest thing I can say has ever happened to me anyway.
It happened about five years ago my brother and I were in our room we share.
It wasn't very late we were watching something on TV and then my mother sticks her head through the door and says, "Steve there's someone in my bed." well me and my brother laughed and said something like don't be daft. Well maybe its dad, "No hes down stairs" she said
The look on her face I could see that she seriously thought there was someone in there. She said that she went to get in and she felt someone in there and thought it was a load of laundry or something under the sheets but when she when she went to move them they were hard heavy and moved.
So I went to have a look but there was a broken light fixture in there that couldn't hold a bulb so I kind of leaned around the door patting the bottom of the bed with my hand still kind of laughing and nervous at the same time.
As I got a little more confident I moved a little closer onto the bed and that's when I touched something that to me also felt like someone was in there under the blanket and no sooner than me touching the mass it moved and turned over, I could feel the weight shift that's when I jumped up and out the door and said yea its probably V===y "My sister" We thought she had gone in there to sleep from her bedroom.
So the three of us still kind of giggling nervously goes into my sisters room to check if it was her. But she was in there sleeping on the bottom bunk bed that's when my stomach turned and we became a little scared and shut the door to my mothers bedroom as much as we could.
There was a hanger on the top of the door inside that was stopping the door from closing completely. We went back to my room and I grabbed a metal bar that holds the backrest to my weight bench up and discussed who it could be while keeping an eye on the bedroom door.
We thought it could be a drunk that had wandered in of the street and eventually we grabbed a lamp and plugged it in the socket next to my mothers door to have a look. But to our surprise there wasn't anybody in there.
Looking back I know there was something in there. My mother didn't sleep in her room for a couple days after but we haven't really thought about it since.
Well like I said not that interesting or dramatic but there you go.
Here are two ideas as to why this thing could have been laying next to your mother.
Theory one: it could be a residential haunting, so the person sleeping may be a type of imprint, when a certain act is repeated it leaves a imprint.
Has it only happened once?
Theory two: spirits are only human, just ones that have left their physical body. Just as a child sleeps with their parents for comfort, maybe a spirit needs comfort or maybe it is out of habit.
Maybe it wasn't aware you were there and your worlds collided.
Has anything else happened in the house, to your mother or to yourself?
Keep me updated:)