TL;DR: my girlfriend said something that upset me, and she said I was trying to pick a fight because of my BPD, I'm not sure how to handle it (both the actual argument and the comment about my BPD) .

So my girlfriend and I are/were having a disagreement. She has a lot of financial trauma, so she doesn't buy nice things for herself. She made fun of my ex-boyfriend because he likes really nice things (kitchen knives, cooking equipment, coffee/espresso, things like that).

I had an issue because she repeatedly makes fun of people for buying themselves things that make them happy, especially when it doesn't hurt anyone else. Personally, I like buying things that I never used to be able to afford. For example, I built myself a really nice computer, since my laptop needed replacing and I always wanted a gaming setup of my own, so I designed and built one.

I expressed this, and said essentially the following:
-that I didn't like that she made fun of someone for doing something that made them happy when it had no effect on her
-that I felt upset and made fun of because I do similar things

She responded very defensively and said essentially this in reaponse:
-she had financial trauma from growing up with two parents who came from absolute poverty (food stamps and everything kind of poverty) and so it was her coping mechanism to make fun of others for what she sees as frivolous purchases 
-she said she felt I was picking a fight because of my illness

Now here's my questions for yall:
1. Am I justified in being upset with her about her original comment?
2. Am I justified in thinking that your own trauma is never an excuse to make fun of others, especially when it literally never affected you?
3. How would you guys go about explaining that this isn't my illness, and that this is genuinely something I'm upset about? (i.e. How do I explain that I'm not attacking her, and that I'm going to hold my ground on this, because it's not my illness)