A.P.
My 5 month old is the same way, he can roll onto his belly but not back again. I think they figure it out in their own time. As far as sleeping I have always read that you should put them to sleep on their back but if they roll over on their own its ok for them to sleep like that so I would just let her be. My son also gets frustrated once he is on his belly and can't roll back over, he screams at me after a few minutes. I always thought belly to back was easier, but I also know babies that only crawl backwards. Don't worry, you're not alone.