Bestfriend suddenly distant now that I'm pregnant again....

My bestfriend and I went to high school together, and were roommates in college, before I decided University wasn't for me and dropped out to start working. I met my husband shortly after and we had our son last year. I just found out I am pregnant again and of course she was one of the first people to find out, but she's being so distant now. She LOVES babies and wants a family of her own one day but with school and her future she has quite awhile (8 years according to her). I'm proud she's developing this awesome life for herself but I can't help but feel guilty sometimes because I'm the reason she gets upset. She constantly keeps saying "I want a baby", "I have to wait 8 more years at least". She even sent a few messages confiding to my husband because she feels like she can't talk to be about it (we're all very close). I tell her constantly to come watch our son and when the new baby comes she's more than welcome to come help when she's free but I know that can't mend it all. Just venting more than anything I guess.