I bought my wife the ring I could afford. It's not a huge stone nor the finest quality in terms of clarity, etc., but it came from the heart and it was the best I could afford at the time. I've since offered to upgrade it numerous times and she's declined each and every time, as THAT ring is the one that signified when I'd made the decision to ask her to marry me and when she said "yes" (bless her heart, her life's not been the same since, lmao!) and as such, it carries more significance than any number of carats could without any thought having been given to them or the ring itself.
I hate that for you that she said something like that, as that's about the most insensitive thing possible. Like a few others have said, I'd take a hard look at whether or not she was the ONE person I'd care to spend the rest of my days with, especially after having said something like that. Good luck and I hope things work out for you in that regards, whatever your decision.