Hmmm... if this is her first child and the baby is only a few months old... right now, that baby is her WHOLE world. Its difficult for a new mother to separate themselves from their babies, so expecting her to want to leave a new baby at home (even though its with dad) to go to the movies or whatever, is a bit unrealistic (I wouldn't leave my son with his grandparents - father not in picture - for any length of time until he was around 8 or 9 months). Right now, you just need to accept that she is in love with that new baby, her entire world has done a 180 and her new identity is being a mom. She doesn't have the time or desire for people or activities that exclude her baby. In time, this will change and she'll be dying for a break from the kid, but right now, a baby that's only a few months old is her only priority. I say just give her some time, she'll hopefully remember later on down the road when she isn't so preoccupied with a new baby that there is in fact a life outside of baby. Also have patience and don't hold it against her or judge her to harshly for expecting more interest out of you. She'll figure out sooner or later what an unrealistic expectation it is.