Alright, in that case, Japonica, either:
A) She thinks that because you have two kids already, you won't be sensitive about babies/breastfeeding in the way that someone who had a hysterectomy with no children might. She thinks that because you have already been through this stage, you will be ok with it.
B) She knows you feel upset about having no more babies but because you also have two kids, doesn't think you will be sensitive about her talking about breastfeeding her second.
C) She knows you are upset but simply doesn't connect her breastfeeding with your feelings of loss.
D) She gets that you are upset about more kids but is incredibly thoughtless.
I offered the first views because I think that sometimes when you have kids already, people don't consider that issues of infertility could ever hurt you.
For example, my friend knows that I've had miscarriages but because I eventually got pregnant and had DS1, always goes on and on about how she and her DH only have to look at each other to conceive! I mean on and on...and I often say "well you are lucky" and then she says "oh well you got there in the end too". She genuinely doesn't mean to upset me, just doesn't see it as at all sensitive for me.
(She does sound sodding boring though, whatever.)