I agree with the other advice here. Make sure she has his teddy or something to sleep with, and when she wakes up, let her play with her own toy in her own crib - don't go in and get her up. According to the book "On Becoming Babywise," babies will frequently wake up and talk to themselves or play for up to 45 minutes in the middle of the night before going back to sleep.
If she is crying and calling for you, give her a few minutes to try to put herself to sleep. I'm not a fan of letting my son cry-it-out either (certainly not to the extent that "Babywise" recommends), but sometimes that is the only way to teach them! So I set a time-limit. I let my son cry-it-out for no more than 10 minutes, beginning when he starts to seriously scream (not when he begins to whimper). Sometimes I give in a little earlier, but I try not to go in before 5 minutes are up, so that he has a chance to try to put himself back to sleep - and sometimes he does. This will probably get worse for a couple of days before it gets better, because you have been letting her out to play and when she doesn't get the reaction she expects, she may raise it up a notch. Good luck!