1) She doesn't have much corporate experience yet, and is drawing conclusions based on her limited experience.
2) She's not in a position of authority... sexism really shows its ugly face when there are power differentials where the woman is on top.
3) She's not yet of an age where child bearing is typically discussed, once she hits her 30's she'll have to deal with this regardless if she wants to have children.
4) Just because you're female doesn't mean you arn't sexist.
As others have pointed out, it is a very small minority of problem people. However, they can have a very adverse affect on an individual woman and her career. Sexism is something we should all be actively aware of and do our best to counter when we see it. It only takes a few corrections (by a male colleagues) to address some of the more prevalent issues -- but you have to do it or the sexism will persist.