My girlfriend puts the milk on the door... Ok, not preferred but not worth a fight. The issue is she puts it with handle facing out which barely fits and even flexs the little band of of plastic holding stuff to the door. If it is rotated 90 degrees it fits perfectly but according to her its "harder to pull out" since you need to lift and rotate instead of just lifting...

Is this appropriate grounds to break up?

/s yes it annoys me but not nearly enough to break up.