My son will be a year old next week and I haven't given him a pillow yet. He's all over the crib so it wouldn't do much good. He had a lot of trouble sleeping from about a month 'til he could roll himself onto his belly. I don't think anybody wants to sleep on their back constantly so we bought a sleep positioner and he slept really well. So if you're not comfortable with her using a pillow when you move her to her own room you could try a sleep positioner and she might get the same comfy results.
I've wondered about this as well (sorry, not a helpful answer ). When my 9 month old would sleep in my bed when she was younger and teething terribly, she would cuddle right up to the pillow, but I always stayed away from one in the crib because I heard it wasn't safe...but I think it's whatever you are comfortable with. I was also told not to have the crib too soft, but ended up getting a twin size mattress pad for under her sheet and she loves it. I figure, if that baby is sleeping, whatever works!!!!
I really don't want to say something negative, but personally I don't think a pillow is safe at 5 months. Her upper body is just not strong enough. If she was to get pinned somehow she would not be able to move herself or the pillow. I think it would be safer to wait until 8-9 months when she will be able to sit up on her own and be physically stronger. I bet she likes it because it feels as if someone is holding her. It could also be the elevated position, she may have less reflux and sleep more peacefully...in that case I would try putting a rolled up towel UNDER the crib mattress to raise the head slightly. Good luck.
thanks for the responses everyone.
we do have a crib wedge in her crib, but honestly she is hardly in her crib. she also naps with a nearly flat pillow. she has not learned to roll over yet, but she does try. maybe tonight i will lay her flat on the mattress and she how she sleeps. she's been sleeping on a pillow for about a month now. and honestly, i can tell she must like it. she sleeps so much better and longer. my aunt is the one who first try this with her, because otherwise anna would not take a nap longer than 20 mins.
gosh, it's so hard trying to figure out what is best for your baby !