So I've liked my friend for a very long time and about 6 months ago she came out of a relationship with a mutual friend of ours. We've always been quite close and just two days ago she made out with me for 10 minutes after we got out of the taxi at her parents house (I tend to walk from there as I live close by). The day after she seems OK with me, we don't mention the kiss but I had to initiate contact even after she initiated the kiss and then today we haven't spoken at all.

I just found out my friend drunkenly told her I liked her the same night we made out and I'm angry at him for telling her but at the same time this could have been the chance she was looking for to find out I like her and for her to kiss me.

If this was true however I wouldn't expect the ignoring she is giving me right now. I suggested we hang out today and she said she'd text me but she never did.

Am I overthinking things? Does she like me or was she just drunk?

A few things to consider are:

Her ex boyfriend is a friend of both of us. She goes to University 2 hours away.

While I have no clue what she has on her mind, or whether she was flirty drunk, I would not be texting her to find out, the coversation would be in person.

You need to ask her as she is the only one who knows.

You say you are getting mixed messages, but you aren't doing a thing to help.
Why do so many people let others do their overtures for them?
Go to her house, knock on her door, and ask her if you can go back to where you were before you got drunk and kissed. If you can, wait a while before you tell her that you have liked her more than a little for a long time, and does she feel the same way. Be prepared for her to say no, just friends.