I'm going to cut off my ex-friend
Why don't you want to see them?
I'm bored of all the things I have been doing with them
It sounds like you already aren't friends with this person. You don't have to keep seeing them if you don't want to. Spend your time with people who are your friends.
They betrayed me.
I'm sorry that they betrayed you. All the more reason to just stop hanging out with them.