I don't agree with people that say just because she wants the diamond ring, it means the relationship is a bad relationship. It's not irrational to feel social

I don't agree with people that say just because she wants the diamond ring, it means the relationship is a bad relationship. It's not irrational to feel social pressure, and feel real pain by not conforming to social norms. At the end of the day if she is happier, that is where she drives economic utility. Just keep at the dialogue, and try to communicate how spending money on something you consider to be unnecessary and imprudent actually harms you emotionally. Hopefully, you will be able to have a nice dialogue and compromise so that you both feel respect from the other person.