It's really not helpful for people to keep on saying about how she'll understand when she has children etc. It makes parents (tbh mostly women in my experience) sound patronising, dismissive and downright smug. It is incredibly hurtful to anyone who cannot have children and makes them feel inferior and like shit. When people say things like that to you, when you are in that position, then it makes you want to end that friendship immediately. And yes, I did that at times.
OP I hope you will find that your friend is understanding and supportive because that's a basic requirement of friends - whatever their own situation. If she isn't, then she's not a good friend. If you are not understanding of her commitments and restrictions then you are not a good friend. That's really the bottom line.
I admit I'm still sensitive about comments made to me before the girls were born. I'd had chemo when I was a teenager and, despite being s scientist, I still have no idea how I managed to have 2 children against the odds in my 40's. I also know that I have friends for whom that will never happen and other friends who conceived quickly and easily. Still more friends don't want children. None of that matters, however, to our friendships. I get so fed up with people only wanting to be friends with either other parents, or other childless people - it really shouldn't matter. The important thing is, not to be a twat. OP you aren't, btw and now is your friend. This is just a blip, hopefully and you will both get to spend time with each other.
Sorry for the essay. Just still bugs me, I guess, to see those silly throwaway comments to childless women.....generally by the same sort of women who then complain when childless friends boast about sports cars and holidays.