are sorority girls nice?

Sorority girls are just like everybody else; some are nice and some are not. Yes, you can be friends with them and do stuff with them, especially if your roommate is in one and you get along. Happens all the time. But you won't be attending members-only parties like with frats or their formal or sisterhood functions. Remember you have to be nice to them too and be sweet and fun and a good friend; if you try to hit on a sorority girl's boyfriend, or talk bad about one member or about the house, you are going to have the wrath of the whole sisterhood down on you and then you will definitely be excluded.