You weren’t unreasonable to ask, she wasn’t unreasonable to say no. If you were upset when she did, then I can understand her seeking some reassurance from strangers that she wasn’t being horrible. Don’t take their responses to heart.
Surrogacy is a huge thing, especially for family, since the likelihood of feeling a strong bond for the baby and not being able to let it go are even higher. She is being sensible saying no.
You haven’t done anything wrong. She hasn’t done anything wrong. I can understand why you both feel sad about this at the moment. When you feel able to, you should offer an Olive-branch. Tell her you completely understand why she has said no, and you respect that, and that you are sad at the situation, not angry at her.
You have a great relationship, it’s taken a knock, but you can mend that. It’s such an emotional subject, I’m so sorry you’ve been through so much, but this would always have been a difficult path, even if she said yes. In fact, saying yes would probably end up doing more damage to your relationship in the long run.
Take some time to heal and then look at further options maybe 