Not that it matters all that much, but I just wanted to say that I agree with everyone else as well.

Ella stays with my MIL for 5 hours a day 4 days a week while I work. My MIL does not watch any other children, so it's just Ella. I am blessed that my MIL was a school teacher for 27 years because she really teaches her so much and I feel it's really beneficial. I worried about this too because my best friends girl goes to day care. A few months ago we had them over to go swimming and Ella wouldn't have anything to do with her daughter. Actually, she cried each time my friend's daughter even tried to touch her. I was a little concerned about it at the time, but the last few times we've been with them, Ella has been perfectly fine. And again, like the others say, they pretty much play near one another, not with one another. So I think you are doing the right thing, try not to worry!