Well, the good thing is...you guys are talking about it and appear to have good communication. Another good thing is that she is clearly aware of what is going on, how irritable she has been, and she has appeared to own her role in the arguments.
Her problem is....she doesn't know what her problem is. She is irritated by something which causes her to have irrational responses to the smallest things. You respond to these irrational responses the same way and it ends up being a pointless argument about who is going to cook the fucking dinner.
How is her work (or school)? Friends? Family? Is she happy about her choices in life? Is she questioning what she is doing? Is she stressed about money? What she has? What she doesn't have? Does she have a little depression? Maybe anxiety? A lot of people in their late 20s have a sort of "mid-life" crisis. Who am I? What am I doing? etc.
She is constantly running at an 8, mood-wise (1 is sleeping....10 is breathing fire). When you are forever at an 8, closing the door to loud will set her over the edge.
She (and you) need to figure out what is going on. If she can not put her finger on it, maybe it is best to talk to a professional...lots of us have done it, and it helps! Maybe look at some stress management activities, like yoga? Meditation? Even running or boxing.
The best thing you have done is make a commitment to her and have realized this is NOT who she really is. Kudos to you, dude.
Things will get better, but she is going to need to work on a little self-improvement....and it may not hurt for you to work on some too. It will most likely bring you guy closer
