Here is something I got off the web:

http://www.critterhaven.org/aggression.htm

Perhaps it will answer some of your questions. I have a 20lb terrier mutt (Fenway) who will growl when I try to take a toy away from him or if another dog trys to take a toy away from him. When we paly tug o war, he growls. He has NEVER bitten, gone after me or another dog or even showed his teeth - he just growls. Because he doesn't go after other dogs or me, I let him growl all he wants. I even growl back.

I would play with her and praise her when she plays nicely. But as soon as she "acts up". I would just stop what you're doing, ignore her and go into another room. After about 30 minutes, I'd go back and play with her. If she plays nicely, praise her. But again, if she "acts up", just drop the toy and go into another room. She needs to understand that her bad behaviour isn't going to be tolerated. I wouldn't swat her butt or even yell at her. I'd just ignore her. I'd like to hope she'd get the picture.

It's a shame she got kicked out of doggy daycare. I firmly believe in socializing dogs and daycare is a good place. Fenway goes 2-3 times a week. If you happen to be able to socialize her with another dog in the near future, I would closely watch them. If she's playing nicely, praise her! If she goes after the other dog while they're playing with a ball, I would separate them and take the toy away from her. After awhile I'd give back the toy. If she plays nice, praise her. But if she "acts up" take the toy away.

I don't know if the above would work. I'm no expert. Did the doggy daycare people have any suggestions?

Good luck.