I know a girl. We made-out while both quite drunk (still capable of being on both feet). Does this mean she has always been keen on me and being drunk just let the beast out?

Could be either. Depends on her level of drunk. If she was drunk and still in control of her senses she probably was attracted to you. If she was totally wasted then I guess you took advantage and she could have been anybody's. Use your senses to figure it out.

Girls are also willing to just make out with any guy who showed decent game or looks hot while drinking at a party. There's tons of plausible deniability, so women will make out and then just laugh it off the next day, claim they don't remember, or joke around with their girlfriends "oh you're so dirty! lol" I'm not sure if women say LOL when they talk to eachother but it makes my point a bit more amusing. Point is, don't misinterpret this as an expression of affection. You want to game her without booze? That's fine, just don't assume you're leaps and bounds in because of that night.

I wouldn't read into it any. Because she may have wanted to make out as a form of release from stress or what have you, or it was an in the moment thing, etc etc.