Re: Feel so sad for her
I think that she should be upfront about her inability to have children and not keep anyone in the dark. However, as far as infertility goes as mamaof3 pointed out, you may not even know if you are infertile until much later in the game and unless you have had tests done, would you like your husband/wife to leave you if you found out after marriage that you could not conceive, would you leave your spouse if you both found out after marriage that they could not conceive?
what about secondary infertility, i.e. you had a child but can not conceieve now, many times it can not be explained as far as why you cant have another kid, what do you do in that case.
I agree with Muzna on the adoption issue also. The decision to adopt is not an easy one and both peopel ahve to be on the same page. It is expensive, you have to have families that would accept the child or be ready to keep family at arm's length to provide a positive atmosphere for the kid. Then there is the societal stigma, not the one against the adoptive parent for adopting whether they have their own biological children or not, but for the child.
as far as the egg donor issue goes, I dont think I have read anything that allows it in Islam...heck forget egg donor, I have not seen any scholar agree to a getstaional surrogacy i.e. if a women loses her uterus due to molar/ectopic pregnancy but can still produce eggs, thru IVF you can make an embryo and have it implant in someone else's uterus. have never seen any scholar even accepting that, and some of their reasons are a bit flimsy. My wife and I have faced many challenges after the loss of our twins 2 years ago so I am very familiar with much of these issues and the current rulings on those.