honestly, if she has always said that and is fairly liberal, i would say there is definitely a chance she will get over it. for parents, it can be a huge shock even if they are supportive. you have spent your child's entire life (and even longer) constructing this idea of what they will be like when they are older, what career they will have, what their family will be like, where they will live, etc. when they come out, it changes that picture. it's shocking. there's also the idea that your kid is going to have to put up with a lot of hate too.
all you can do is move forward. you're going to deal with people being shitheads, but you'll also find some people be really supportive. whether your mom comes around or not, you are not alone and you can make your own happiness!
while my parents were supportive, my grandparents are pretty homophobic. i know it hit them really hard, and they were dicks about it, but it has been 4 years now and they ask me how i am and if i've met anyone. they used to just ignore it and not talk about it. sometimes it just takes time.