Gf asked how I make my oatmeal

Hey I’m new here ..but just wanted some insight..usually in the morning I (29m)go to the gym this morning was no different but my gf (34f) wanted to make me my breakfast which is just oatmeal and peanut butter..so she asks” how do you do your oatmeal” I tell her in the order “I open the oatmeal Pour it in the bowl ..” But before I eat to my next step she like why are you talking to me like that and I’m just confused like what do you mean...she says I know I have to open the oatmeal why would you tell me that ..I was just going down the list of how I do it ..she calls me a asshole and narcissist ...I really didn’t mean anything by it I get so I apologized and we made up but I was so lost