Listen, the incest and paedophilia comments aside (which are enough to end a friendship), you don't actually owe it to anyone to be their friend. Especially a person on the Internet that you've never actually met in real life. I mean no offence but I personally don't see purely online friendships as "real" friendships because to truly know someone, you need to know them in real life and to see them in all kinds of different situations.

But regardless, friendships should be a choice. We can't choose our family, colleagues or classmates, but we can choose our friends. You are right that in order for a friendship to work, you need to have similar interests, beliefs and values. If you don't have that then the friendship simply can't work. Don't feel bad if you don't want to be friends with someone. You don't have to be rude or mean but you don't have to force yourself to be friends either. You shouldn't have had to delete your whole Twitter just because of that girl. You could have just said to her that you don't think the friendship is working. Wished her all the best, then blocked. You can block her E-mails too. Life is too short to waste on people you don't actually want in your life.