Should I 21M forgive my best friend 22M friend for kissing a girl 20F that I was talking to?

Should I forgive my best friend friend for kissing a girl that I was talking to?

So basically I met this girl 5-6 weeks ago and we started spending a lot of time together because we live in the same apartment complex. We liked each other and we were sleeping every day at each others doing different stuff. However, I did not like her as much as she liked me tbh. She was a cool girl to be friends with, but I just could not see her as a potential long term partner for different reasons (values, life, interests,etc.). I could tell that she liked me a lot and caught feelings. She started getting mad over not replying her texts and would message me good night and good morning texts every day and would tell me she misses me every day as well.

I did not tell anyone about her, but my best friend. I told my friend that I liked her, but the biggest red flag that I could see in her was that she can lie sometimes explaining it that she doesn’t want make me mad or lose me. Everyone knows that i hate the most when people lie and I explained that to her. The problem that I also saw that she drinks like 3-4 times in a week (we are in college). So I started distancing myself from her last past week. So a week ago I told her that i do not want to have to do anything with her in sexual way and would prefer to be friends, to what she got extremely mad and started crying like crazy. At that time I was with my best friend at my place(we all live in the same apartment complex) and at that time i told her to come over and talk about it. I tried explaining it to her that I like her only as a friend, but she started even crying more and my friend told me he can talk to her if i want and explain her that me myself is hard to date and that kind of stuff so she gets reassured and maybe gets over it. Tbh I always knew from the first time i met her that she would be my friends type so I told him that you can shoot your shot once she over me.

However, 4-5 days ago she came up to me and talked to me that she will change and stop her drinking and will change for better to be with me to which I agreed. Basically, we chilled and hung out couple of times after that.

2 days ago I flew to another state to meet my famly while all they stayed in the same place. So yesterday my best friend went out with my other friends and saw her at one party. So he calls me and asks if i mind if he shoots his shot to which I said NO. However, the catch is I forgot to tell him that we started talking again and he thought we are not talking anymore. Then later in the night he calls me drunk and asks again to which i thought that if my best friend likes her more then why not so I said yes he can and I explained to him that I still like her but it will be a test for her loyalty(which i know is very bad). So he made his move trying to kissing her to which he pushed him away and said that she can’t because of me and she can’t kiss my best friend. And what pissed me off she said that if i did not exist maybe shed give it a shot. So later in the night my friend called me and told me everything about it. Then, she also texted me that she does not homie hop to what I said why did you tell him if i did not exist youd give it a shot to which I she replied she did not say that. I knew for sure that shes lying again and my best friend never everr lies to me. I told her that i will end everything if I find a proof that she lied to which she admitted she lied to not make me mad and that at the end of the day I still exist. I told her that i do not keep the liars around and blocked her everywhere. Then my friend calls me later that night and tells me that she told him to come over so he can help her fix everything and call me through his phone. I told him that i do not care at this point, but I told him that I changed my mind and asked him not to have anything to do with her. The later throughout the night she kept calling me from his phone until 8 am.

When i woke up I called him and asked him about why you let her-call me so many times and why he stayed there until 8 am to which he said she was going crazy and was telling him that she would hurt herself if I do not forgive her. After all that he tells me that they at the end kissed for a moment , but stopped because of me and she told him that she still likes me. He apologized a lot of times andd even cried at one point to which I asked him to give me some time.
Now, i know I am also not the best person and I first told him yes he can then said not to do anything. I am trying to be better.Just please tell should i forgive him or her? Because deep inside it also hurts that she kissed him and he did that.