Maybe she is trying to identify with you? You have trouble sleeping so she is talking about trouble sleeping. What other subjects do you all have in common? What did you talk about before she moved/had a baby?

I would simply say something like, "I don't want to talk about how tired we are, let's talk about __________". I would just redirect what you talk about, let her know you are not interested in talking about being tired or babies :-) I think that is all we can do about what other people find interesting to talk about; let them know we are not interested in that subject, how about this one.