Honestly, if she's genuinely busy - with work, school etc - you shouldn't be that mad about it. My girlfriend did that for the last month before I broke up with her and it PISSED me off. I would be like "What the fuck I'm working 50 hours a week to pay for college and going to school and you're mad I don't have a lot of time for you?" I'm not sure if the reasons are similar, but if its legitimate don't be mad.
On the other hand if she seems to be blowing you off then assert yourself. Tell her straight up " I feel like you're neglecting me." If she takes it the wrong way you can always salvage it. That's the beauty with women (at least from my personal experience), there's always time to change how they feel

Unless you fuck up bad of course.
Why do you guys fight? People have busy lives - a relationship should be a positive, beneficial thing for both parties. It's meant as a crutch, someone to lean on and love, not as extra stress, even though that's what tends to happen so much. Think about why you fight, if the reasons and really dumb then just agree with her - you don't always have to be right.
Again, on the other hand, if you guys always fight and it is never resolved, it might be time to give an ultimatum or end it.
And I'm a big fan of sex, sex, sex. If things are going bad have GREAT SEX. It really works fucking wonders!! Trust me you'll see. Get her in the mood, and have awesome, amazing, spectacular sex. It'll change everything for at least a day.
Today I was talking to a very, very attractive girl who I'm friends with and hooked up with a while back and she specifically told me "When we don't have sex for a couple days I feel anxious and tense like uhhhhh I can't describe it but sex always makes it better." Those were pretty much her exact words. (We as in her and her boyfriend - it's not the girl i posted the question about either:).
So ya, suck it up and see her and have awesome sex to resolve conflict. If nothing seems to work - tell her your feelings, maybe you guys are just getting sick of one another? You seem to be at the point where you get mad at little things (I've been there.)
If she was some sexyass girl you were trying to bang and she was too busy for a week or 2 but then wanted to hangout would you be mad? Nope, probably be elated. Think about it that way.
Goodluck mate! Hope something I said helped, had to rush it sorry.