Can you talk to your friend about her sarcasm? When someone is hurting, sarcasm from someone else can be hard to take objectively. And this can cause what the person is really saying to be misinterpreted.
I'm really glad you are going to give your friend the benefit of the doubt. It's important to keep in mind that someone having a different opinion about something doesn't necessarily mean they are trying to invalidate you. Yes, it does happen, but if your friend has been a good friend otherwise, it's good you've decided to give her another chance.
My sister and I "agree to disagree" all the time. (That means, we just have different opinions about things and we don't fight about it when this happens.)
--Ceara1010