Tummy sleeper

When my baby girl was 3 months, she rolled over to her tummy for the first time. She will only roll on to her tummy if she was laying in the floor. She’s is a side sleeper when she’s in bed. Now she’s 4 months. Last night she has been rolling into her stomach and sleeps. She does have her head turned on the side, so she can breath.

Is that okay for a 4 months to sleep on her back then during the night whenever she rolls on to her stomach and sleeps?

I’m worried abt SID.