My wife wants to divorce me because I bought her a “cheap” wedding ring.

We have been together for 8 years now and for the better part of that time we’ve been saving to get married. Most of that money was spent on the wedding and honeymoon. I wanted to include a ring in the budget but she said it would be too big of a hit on the budget and she was fine buying a nice one on her own. Well the wedding happened and she announced she was divorcing me because I didn’t buy her an engagement ring and it made her feel like she was nothing to me. I am in shock. I had no idea she cared so much about this. I love her and it hurt me that she feels that way. She wants a divorce and I have no idea what to do. I would buy her a ring if it would change her mind but she says it’s too late. What can I do to save our marriage?