An Uneasy Milk Request

So I know the title is really weird, but it was the best I could come up with. This... Super freakish thing happened to me the other day and I'm actually afraid of my sister's house now because of it.

To preface, my sister had closed all the blinds and you couldn't see inside their living room. Her car was also in the driveway.

A few nights ago my mom and I were cooking dinner, and my mom asked me to walk next door to my sister's house and ask for a cup of milk. No one in my house drinks milk regularly, so we don't tend to have milk around. Anyways, I walked over and knocked on their front door. The dog started barking, and I heard someone inside talking. A woman was saying something about my nephew. I genuinely thought it was my sister. So I knocked again, the dog kept barking (from my sister's bedroom, on the other side of the house, despite that he had full reign of the house.) and I heard the woman talking some more.

I stood there and kept knocking for a solid 5-6 minutes, getting mad and starting to yell at her through the door. Finally, I gave up and walked around back of the house. I walked in through their back door because the knob is busted and it's always unlocked, and I went into the house. Only to find no one was home. I checked every room, even the creepy basement, and then I looked at my phone, she posted a picture on facebook at the time of the talking in her house, of her and my nephew out to dinner.

My sister did ask if her dog might've hit one of her son's toys, because obviously, a clean house and a toddler don't mix. But I distinctly heard the voice mentioning my nephew's name. My sister freaked out and started yelling when I told her, in her living room, yelling at my grandmother saying she was going to get the house exercised if she didn't cut it out. (Something we all laugh about now, because my sister is terrified of anything paranormal.)

This is a some what unrelated note, but while I'm typing this, there's a shadow moving around in my parent's room, which is almost at an angle from mine, and I'm the only one home. (All three animals in the house are at the opposite end of the house right now.) I am just a little unnerved by the movement. Not sure how I should feel right now, since what I'm typing and what's happening are like... Maybe linked? Scary to think about.