Nah, I think that the above was just a 'symptom' of something deeper going on for her. In other words, she got triggered by something, presumably from her past, and that innocent act (you staying at your mom's) set her off.

Her reaction (tears, afraid that you will break her heart) says it all. Her sense of emotional security was probably severely compromised or betrayed in the past by a significant other... or others. Hence her knee jerk reaction and her erroneous 'interpretation' that you choosing someone else (i.e. your mom) meant a repeat of said perceived rejection or abandonment that she may have experienced in her past.

I would be gentle and more importantly reassure her. Then maybe if she feels safe with you, she will be able to share more what this is *truly* about.