She'll get over it. My mom was actually the one who was more uncomfortable with me being gay than my dad was, which you usually hear the opposite of, especially for guys. I think it had to do partially with my dad's sister being a lesbian perhaps, but my mom cried when she found out and my dad laughed at her.
Don't worry though. The fact that she didn't lash out at you and basically tell you to F off is a GOOD sign. She'll warm up to it over time, especially if she wants to have you in her life. I sort of came out by accident to one person in my family, and within three days my entire family (some extended included) knew about it. It was a terribly invasive way to come out, but I'm glad it happened I guess.