What I personally would do is to just not apologize and see what she does. Does her mood improve eventually anyway? Does she escalate further, all the way to breaking up?
Anytime I see this kind of pattern I have to jerk it around a little to see what’s up. If something like this is enough to provoke a breakup, then I would just let it happen and then find a new girlfriend. Life’s too short to have to walk around on eggshells all the time.