6 month old sleeps in a rock n play

Ok so I have a tiny 6 month old and she has been sleeping by my bed every night since I brought her home in a fisher price rock n play, it works so well for her , she sleeps 9 hours every night and falls asleep with in 5 mins , I just wondered if I am a terrible person for keeping her in that position like that all night now that she rolls and can lift her head ....should she be in her crib now to allow her to stretch and move freely ? I mean they say at 6 months the risk of SIDS goes down tremendously but she is also not even 12 lbs yet and still fits snug in her rock n play where she seems cozy but I have noticed she stretched and arches her back like she wants to roll around but cant and I wonder if I should just let her have her crib to do so...basically just looking for some thoughts ...advice...suggestions...idk I am ftm and wondering if anyone else's LO sleeps in a rock n play?