Is there harm in doing this, co-sleeping question.?

My daughter is 3 months old.She has really started sleeping well at night (6-8 hr. stretches) which is REALLY good from how it used to be during her colicky days.By 8-830 she is ready for bed, there is no keeping her up later or she gets mad.So she falls asleep great in her crib and is normally out till atleast 3, sometimes as late as 430 when she wakes to eat. After eating, she is wide awake even though I keep it dark, rock while feeding, etc. I have tried to soothe her back to sleep and it doesn't work. She gets upset quickly when put back in crib. Last night I spent an hour going back and forth reuring her.She would fall asleep and 5-10 min later be crying. So as always, I give up and pick her up and we go to my bedroom and she falls asleep in bed w/ me.I have tried doing her light show/mobile/etc in crib or play the lullaby cd, that just seems to wake her more and she wont then sleep when she gets to bed w/ me.What would you do? I WANT her to fall back to sleep in her crib.