First of all, you should start out as friends. Get to know her like what she likes and what she doesn't like. Start conversations centered around her and be a good listener; people love it when you do that and you'll earn her respect pretty quickly.
Then from there, I can't exactly tell you what to do because it's always different. If I were you, I would try being there for her and focusing on her wants, but not to the extent where it looks like you pity her. People hate being pitied. You have to somehow show that you deeply care about her. That will usually help you get someone to like you, because they feel good or special around you.
Unfortunately, there are no guarantees that this will work. It often does work, but sometimes, due to certain circumstances, it doesn't. Don't be discouraged by this. I just want you to keep that in mind, so nothing would surprise you too much and it diminishes a lot of possible pain.
