Just make sure she's got lots to do when she gets to her tummy (toys in view, things to look at) and when she does want to get back to her back, then help her get there, but also show her how to do it. My daughter would always get stuck on one arm, so we tried to show her how to tuck her arm under and roll. Basically, it's really something they have to learn for themselves and they're going to get frustrated for a little bit, but she'll figure it out soon enough -- and then you'll be wondering where this mobile LO came from!