Toxic friend

So I am wanting to discontinue a friendship and I really don’t want to have that conversation with her because she never admits or realizes when she is in the wrong, and I don’t know if I should just bare through the conversation or just ghost her until she hits me up? Let’s call her Norman. She has been one of my bestfriends for like 4 years..we’ve been on and off because whenever she had a boyfriend she wouldn’t hit me up until they would break up most of the time. She has also been really good friends with my ex for even longer. She hooked me and my ex up ( we dated throughout highschool and r working on getting back together but this all happened before we decided that) and we all three would always hangout. Me and my ex have been broken up for a year and Norman just started hanging with him again. She has also recently started being friends with this girl in our town who we all know... Let’s call her Hillary. Norman invited Hillary to my Ex’s party for the 4th of July ( I was in a diff town celebrating). Hillary, my ex, and I all went to highschool together , had the same friends and nothing ever happened romantically between them and they’ve never flirted before. But at the party everyone was drinking all of a sudden Hillary started telling Norman how cute he was and all this stuff. Norman kept telling my ex what Hillary was saying and told him to go kiss her and stuff but he thought that was weird cause he is shy about pda ..even flirting infront of people he doesn’t do . But she kept on insisting for them to kiss but they didn’t. She even told me she told them to kiss but I was too shocked to express my feelings about it. The next night the Hillary was having people over and Norman BEGGED my ex to come and the entire time was trying to be a match maker and get him to hook up with Hilary because she really wanted to...they all started drinking ...and they did. I just feel so betrayed by Hilary.. I’ve had her back so many times and been on her side when no one else was ( she even got in a physical fight with my other friend and when I had to choose..I took her side on it, I’ve stuck up for her when people have bullied her ) She knew that this situation would hurt me so much, yet she encouraged it . If she had my best interest at heart she would have shot the idea down and not feed into it. Even though he can make decisions himself I do believe if she wasn’t involved, being the matchmaker, it wouldn’t have happened because their paths wouldn’t have crossed if it wasn’t for Hillary, and my ex never makes the first move on people in a party setting. She’s let me down so many time and this is the last straw I don’t need her as a friend if she’s not gonna have my back like I’ve had hers. I feel so burned by her I don’t even want to let her know how I feel because I know she will just excuse herself