Bad babysitter or am I paranoid?

My 7 month old, Ava has been with the same sitter since 6 weeks. She came highly recommended. At first things were fine, around 3 months old I told the lady I may get off early and if I did I would get Ava, she said be sure I called first, I felt this was odd but my mom said she just wanted to have her ready, 2 days later I dropped by at 9:30 without calling just to change Ava's outfit, the lady was alone in the yard, she was very surprised to see me you could tell, she said she was just checking the mail while the kids napped. She said she would take the outfit and change her later but I insisted that I see Ava and change her myself, I walked in and Ava was sleeping wrapped up in her bed, I woke her just to be sure she was ok, she seemed ok and I left though thought it was odd that all the children who don't arrive till 7:30 would be sleeping at 9:30. Again my mom said I needed to calm down and get a grip. I tried to let it all go and not be so paranoid, but in the last month Ava has become so withdrawn that my mom who rarely gets concerned has worried, Ava rarely laughs, she makes small noises ever so often but never loud and she rarely cries. I had her hearing checked and she is fine. Her dad and I work with her and try hard to get her to smile and laugh but it's rare that she will do either. My mom and I did an experiment this past weekend, I fed and changed Ava and put her in her bouncer in her room and mom and I watched at the door to see how long she'd sit there without crying, over 3 hours past, I was almost in tears because to me that's not normal. I'm afraid she is just thrown in a crib and paid no attention to allday. She has no social skills at all. She doesn't try to to anything babies her age do. Last night I heard of a couple that toke their 2 children out of this ladies home before Ava started going because their youngest was doing what Ava is now. The oldest one cried when they toke her. Their dad(a state trooper) got suspecious and drove by her house every 10 minutes for an hour one day and everytime he went by the lady was working in the flower beds in her yard. Needless to say he pulled in and toke he's kids who were inside alone with the other 4 kids she keeps all under 5. I guess my question is am I being overly concerned? This is my first child. My mom has agreed to keep Ava till I can find another sitter, although the lady doesn't know I'm trying to find somebody else. I worry she mite have druged the kids, should I speak with other parents there? Should I have Ava looked at by her doctor just to make sure she is ok?