<human>: Could you distill the essence of the text into 1-3 sentences?

Let me start off by saying I'm friends with all parties involved. Good friends with the boyfriend and friends with the girl as well, but obviously closest with my best friend. Anywho, they have been dating for over a year now and have had troubles but honestly are a great couple and I know they love each other more than anything. The guy would honestly do anything for this girl. He has a problem when he drinks, where he gets way too drunk to the point where he is just completely out of it.  Fast forward to last night, one of my girl friends told me they kissed (for what she said two seconds) and then quickly stopped and a party. I was at the party and I know both of them were some of the drunkest I've seen them. But I was still shocked.

When she told me this (yesterday) she had also been drinking a lot, as had I, and we were all out with friends (best friend wasn't there). I got visibly upset and pulled my friend's boyfriend aside and asked him if it was true and he had a huge look of shame on his face but didn't say anything. Now, we were out with friends at a local music festival so we were all pretty drunk. I ran into my two other friends and they saw I was upset so I told them what happened and asked for their advice. They told me to tell my friend (they've met her once).

I feel like if I were her I wouldn't want to know.  I know how much he loves her and while I do think he needs to be sat down and talked to about his drinking, I think this is a stupid mistake that she would probably rather not know about as long as he stops drinking. I (stupidly) ended up telling like 3 people about it because I didn't know what to do and I was drunk, and I wanted advice. So now I'm concerned it could get around to her as a rumor (she goes to school about 3 hours away but still comes up to visit about once a month). 

Do I tell him to tell her, or I will? Do I let it blow over?
<bot>: Dumb drunken college students. Best friend's boyfriend kissed another girl very briefly. Good friends with all parties involved. What do I do?