There's a ghost in my house.

I think I saw a ghost in my house Friday night. I'm sort of freaking out. Now, I can't stop looking for it or thinking about it. Here's what happened...the girls were in the living room playing on the computer while I was in the kitchen cooking/blogging. Husband is out (of course!). I was sitting at the kitchen table facing the window. It was dark outside. I could only see the reflection of what was behind me in the kitchen. Our neighbors are about 15 or so feet away and, if their lights are on, I can see in their house. I happened to look up from my laptap and thought I saw them. But, as I was squinting wondering why they seemed so close, I realized it was a reflection and for a split second thought it was one of the girls walking into the kitchen behind me. I was seeing an arm (the curtain was obstructing much of the window) with a long black sleeve and a ruffle on the end, and I could make out a hand, as if this person had just walked into the kitchen! Then, I realized neither of my girls are wearing black and I jumped up and turned around to see nothing. My heart was pounding and I was scared to death! I sat in the same exact spot at least a dozen or so times trying to figure out what I really saw. Of course, it must be my imagination, strange reflection, something else, anything else. But, it's not there. I haven't had any bad vibes about it or felt that creepy presence of someone in my house, so I'm not afraid to be here. I'm just freaking out! Some people have said to have the house blessed, or talk to the spirit. "Yeah, uh, can you please pass over, and never scare the crap out of me again?" I don't know what to do! What would you do?