I can understand it must be difficult to have a friendship when political views are diametrically opposed, especially if it's hard to find subjects to talk about that do not link back to politics in some way.
For me the politics would just be a matter of difference of opinion, and I'd try to find other common ground or agree to disagree on politics, or agree not to discuss at all and stick to other subjects. The bigger issue is the racism. I see this as an attitude problem rather than a different political stance. I can get along with people who have different political views to my own, who are religious when I am not, who have lifestyles nothing like mine. However, I would not want 'racist' 'friends' - the two do not go together, they are like a poem that doesn't rhyme and this sort of bigotry rubs me up the wrong way, leaves a bad taste, a bad smell, a suffocating atmosphere that I don't want to live with.
I can tolerate a lot of things, have had friends that make inappropriate comments or jokes. Once had an Irish mate that politics was a no-go subject with as some comments she made early on meant I strongly suspected I would disagree with her!
If you really don't want a friendship with this person you either have to totally ignore them, tell them how you feel then ignore them, or give them a blast on why you exercise your right to choose your friends and do not wish to include a racist (like her) among them and if she continues to 'bombard' you with calls, texts, messages on groups, forums, on your phone or online etc you will put a 'call-bar' on her number, block her, delete her, ignore her anywhere else in life. If she persists even then, inform her that the harassment will become a police matter. It would drive me insane if anyone bombarded me with anything - real friends would not do this.
While everyone is entitled to their opinion - even [and this may make me sound rather judgemental] Trump-supporting racist twats, I would not want them in my life or to count them amongst my friends. Good luck