I agree, it is asslike to the other person to switch up on something like that. But it's pretty major and it happens. Maybe to her having children is more important than the relationship. I don't think it's willy nilly..very hard decision. It is unfair to the other person but you gotta look out for yourself first and decide if it's more unfair to you to be in something that you dont want and will regret forever, I don't think that would help the relationship either. This reminds me of Friends where Monica has to break up with Richard who is in love with because she wants kids and he doesn't(although they werent married).