Maybe you're not capitalizing on her wanting to be by herself. She will sometimes want to play by herself, even if she doesn't know it. I've noticed that when my daughter is particular fussy about my play, (telling me how to play, getting very quickly upset, etc. if I'm not doing it exactly the way she wants me to do it) most often, she probably needs to be by herself for a little while. When that happens, I just make a quick excuse to pardon myself from play, (I have to go to the bathroom) and soon, she will be playing on her own. It took me a little while to recognize when she WANTED to play vs. when she THOUGHT she wanted me to play. Kids need to play by themselves, but might not be able to dis-enguage when it's needed. Sometimes, the loss of a playmate is hard for them if they are already upset so seeing the cues are particularly important early on in play, or you could be facing a meltdown. Also, something else that cound work, I've found that if I play an hour with my daughter, I'll tell her that I have to do dishes, or make supper, etc., and she'll have to play on her own for a little while, but if she wants, she can come play with me, or help me make supper or do the dishes. She usually prefers to be on her own, but sometimes, I'm surprised when she says that she'll help me. It's give and take. Good luck, I know it's hard when you're their friend, and a parent. Just think what we have instore for ourselves and they are teenagers, when they need a parent that they can trust like a friend. Yikes!