Baby keeps flipping on to her tummy at night

My baby is about 5 months old. She can flip from her back to her front but not the other way yet. She always goes to sleep on her back but in the middle of the night she will always flip and sleep on her tummy quietly and would sleep like that for hours. If I do wake up and check on her, I’d flip her back on her back but she always flips onto her tummy to sleep. I think she’s more comfortable that way. I read that it’s not good for baby to sleep on their tummies until they know how to flip back on to their backs by themselves. In such situations what should I do? Should I just let her sleep on her tummy at night? I can’t be awake the whole night to keep on flipping her.