I had similar thing with my mum getting a bit too overbearing on issues, especially late nights, the important thing is to make her trust you. Ie, get your friends to come over for a sleepover kind of thing and that way she gets to know who your going out with! tell her where you are going and, as unreasonable as it sounds, try phoning her every two hours or so (although only up until 12 ish or she might get more mad) to tell her your ok. It's probably a bit late now considering you are off next week, but it's never too late to make her feel more wlecome in your life, maybe that way she'd loosen up on things. while your at uni it would help to send her emails or letters saying how you've got on, or set up a myspace so she can see the pics (obv only put nice ones up!) and read how you're getting on at uni. This is how I made my life easier anyway it may or may not work for you!
as for her disowning you, it's called the heat of the moment, I've been "disowned" about 50 times before I started improving links with my mum, and I'm fairly sure she would've hit me a couple of times had I not been bigger than her!! and yes i know hitting kids isn't supposed to happen but it's not like it was entirely unwarranted bcos you did turn up at four in the morning!!