I still think she is being insensitive. Even if she had to go through IVF for her baby she doesn't need to carry on about it in front of you. Even if she is super excited about it, if other people are in the room that are sensitive to the subject then I think she should politely not talk about the subject so much. She has the other 29 days of the month to discuss pregnancy talk. I don't talk about pregnancy stuff in front of my family, it would make them uncomfortable!
Now once her baby is here, there will be nothing you can do to stop the excitement. Everyone will be looking at the baby. Hopefully once you see her little baby you will also be very excited about it and want to hold him/her and all of that. But for now I can see how this would be a very sensitive topic for you.
I hope you will get pregnant real soon and then the two of you can both be excited together. Until then I guess it is best if you just try your best to be happy for her. If she is mean or rude towards you then honestly if it were me I would not see her for a while. I would say I was not feeling well and avoid the family gathering until I felt like I could emotionally tolerate being around her.