Maybe it was just you are not very comfortable around children. My daughter is grown and married and on her own and has no children. I find when i'm around a friends grandchildren I'm just not sure how to talk to them. It's just been too long since I have had to deal with children. It leaves me feeling awkard not neccessarly jealous.

Even if it is jealousy, give yourself a break, we all feel that at sometime or another. The more time you spend with your friend when her daughter is around most likely you will start to be more comfortable.