Okay ladies, I need help! My daughter will be 7 months old on Sunday and she doesn't do much tummy…

Okay ladies, I need help! My daughter will be 7 months old on Sunday and she doesn't do much tummy time. She's always hated it. For about a week or two this month I was able to get her to do about 30 minutes straight a day of tummy time. But all of a sudden she went back to hating it. She knows how to roll over and the second I place her on her tummy she rolls onto her back. She does this EVERY time. I place her favorite toys in front of her while she's on her tummy and she just grabs them and rolls over onto her back to play with them. I tried placing a mirror in front of her and everything. She just rolls onto her back. I tried rolling up a towel and putting it under her chest and she still just rolls over. What can I do?! I want her to learn to crawl! Thanks in advanced!