I agree with what everyone has said. The first thing you need to do is gain her trust.
When we got our warmblood he was a nasty piece of work and didnt want human attention at all. We spent time sitting with him while he ate, brushing him while he eats, talking him for walks and doing as much as we could to show him all we were going to do is fuss over him and love him.
Spent a lot of time with her. As kelly said tie her up to brush, pick feet etc. if she isnt into bring brushed everywhere just get a little further each day. Even if it takes you a month to be able to brush her belly then so be it. To you she might be vicious but to her she is protecting herself from possible harm. You have to work hard to be the person that she knows for sure is not going to hurt her.
Don't rush anything. Go at her pace. You have all the time in the world. While she feels comfortable keep going but as soon as she isnt comfortable anymore stop and do something she does like.
Always remember that to her you are a predator until you prove yourself as a friend.