My (25M) fiáncée (24F) spent $900 on a stupid handbag

I have been with my gf for 9 years. We are engaged to be married and have been saving up for a house. We live in a moderately expensive city, but I make good money making over 130k a year. My fiancée would have gone to medical school but she decided she wanted to be a flight attendant bc the hours were better. She still makes a fair amount though. <br><br>Anyway we have been saving up for a house and we are finally closing on one in about a month! We decided to go on a nice weekend getaway to Miami to celebrate before life gets crazy. We decided to walk arround Miami on the first day we were there and see all the sights. We walked past a designer store, and my fiancée stopped and said “oh wow, they have a new bag out!”. I said yea it’s cute but why would you ever spend that much on a bag? She said she wasn’t going to buy it. We kept walking and then I had to use the restroom. I told her to look at the stores over here while I went to the restroom and she said “perfect I’m going over there actually”. I didn’t think anything of it. I came out and she had a huge bag and smile on her face. I asked her what is that and she said it’s the purse. I said “that’s a stupid waste of money” and she said “it’s only like $900”. I told her that’s not only and she said it’s not my money if I saved up for it it’s fine. We had dinner and it was awkward and she wouldn’t let me get her dessert. I wanted to get her a nice dessert but she said no I’m going to treat myself. I found out she spent another $400 on dessert and drinks and I accused her of trying to make me feel poor and she got all mad and said I was putting her down. We have been fighting ever since. I told her I wasn’t going to marry her if she doesn’t get her priorities straight. I told her to sell the purse but she won’t. She keeps giving me examples of all the times I spent “stupid” money but this was the most she ever spent. I don’t think she understands how much money that is. Should I just let it go or demand she returns it?<br>TL;DR: my fiancée spent $900 on a purse and won’t stop trying to make me feel bad for pointing out it was a dumb purchase