I think it's normal to be sad when a meaningful relationship has to come to an end, and it sounds like she is trying to be honest and explain to you her situation so you can see her reasons for having to say no.
It's just all around sad. But I do agree with satsuma. There is a joy in that you both have shared this caring relationship. That is a good thing. Everything ends, everything. But it still has beauty and meaning. And you will carry that forward with you.