Nothing... until you're sure you could really date a girl. Give it some time to see if it's just a little crush that will pass, otherwise you risk really hurting her (falling for a girl who turns out to be straight who is just experimenting on her would be hell for your friend). You could lose a close friend, and altar the dynamics of the whole group for nothing.
Give yourself time to be sure...
...and making out while you're drunk is sloppy. Everybody can like someone drunk. That's when people make their WORST decisions. How do you feel sober?