Why would a girl treat a guy like crap out of nowhere?

I suppose if there were feelings hurt, you did something to annoy/piss them off, or you weren't taking the hints about them not liking you or not wanting to be your friend any more, that could lead to the cold shoulder. That being said, it's kinda hard to gain any context to the situation with such a vague description by the OP.

She could be trying to get you to dump her? I know a lot of girls aren't really comfortable with doing the dumping, especially if there's no particular reason for it other than 'I just don't feel it anymore'. Chances are, it's not 'sudden', but just something that escalated over the course of your relationship. I think it's more likely that it's a misunderstanding though. Regardless, if it bothers you, you should try to talk with her. Seriously discuss your relationship.

People don't treat friends like shit so I'm kind of amused how some still bring the friendzone up. This will sound pretty harsh but it's the no-interest-no-not-even-platonic-zone you're in. People treat other people badly to distance themselves from said people without having to actually confront the issue. It's cowardly but usually effective. You can wait it out since it indeed might just be a mood thing but don't get your hopes up.

To be honest I have no idea why do you still keep talking with a girl like that. Just leave her alone with her behavior. There is no reason for you to stay there.

This reminds me of recent events with my friend he just broke up with his partner but cause she slept with another man which was my friends best friend and when my friend ex partner for busted she lifted her hand to him my friend treated this woman like a queen and done everything for her but when ever he was being his self she would always hit never the less he is alot better with out her and I'm going to help him get revenge I know two wrongs don't make a right but these people that has hurt my friend deserve it

Depends. I often get accused of treating guys like crap for no reason. But in reality it is a very good reason. For girls like me who have been victimized repeatedly, we might be defensive and a tad aggressive. It is not that we hate you, you might remind us of someone whom hurt us, and to protect we are pretty much a-holes. But then sometimes an a-hole is an a-hole, regardless of gender Just think of it this way girls and guys are the same we just have different parts. try to think of why a guy would be a dick to a girl and you get your answer

Personally, I'm the kind of person where I don't let people treat me like shit and think they'll get away with it regardless of gender, mostly because I'm a hothead with the blood of Vikings coursing through my veins but most of the time people just aren't even worth the time or energy for that, so I just cool and drop it and make an effort to avoid them. It might be a mood thing they're going through where they've hit a bump in the proverbial road of life but then again, they might just be dickheads. Nonetheless, they're best avoided at all costs. But in the case of relationships, it's worth trying to talk about it and understand their situation a bit more. If it's a misunderstanding and they're sorry then cool, but if it's genuine spite then; in the words of William Shakespeare - "Fuck it" (I wonder if anyone will pick up that reference.) and just don't bother with them anymore. If they're going to be like that then you're better off with someone else.