/biz/ - Business & Finance

For context: she's my first gf ever. We are both older than 30 and live together from the start of our relationship.
She said that I should be more generous with her, that I usually charge her half of what we spend (which is true, but also she offered to pay the last couple of times we went out, and most of the time she buys the more expensive, unnecessary stuff, so... ???), that I don't even buy her the desserts she likes and that it's unjust that I make double her wage yet still make her pay her half. This is all true, BUT in general I usually spend more than her. Part of her argument was that I'm good at maths and she isn't.
I've never denied being a miser, but I've always explained to her that I was born poor, I lived a shitty life and that I would save as much as possible until I get to buy my own house. I also told her when we met that I'd buy a car in the future and a house or at least an apartment if possible, but I haven't done so. She keeps talking about a car and shit.
Is being a miser a sin? Should I tell her to part ways? I felt enraged at first, but now that I think, maybe I should just tell her that I'm NOT gonna change, so she decides our future.

(cross-posted from /adv/ cuz I want to hear your opinion too, /biz/)