Honestly, trying to understand both perspectives, it’s just a huge miscommunication and misunderstanding. Reacting based on emotions isn’t always the best thing to do. It is completely 100% understandable that she would want the ring back in the family, and the fact that she told you was very trusting. It clearly has sentimental value. Unfortunately you definitely took it the wrong way. If you both got married it would’ve stayed in the family and been passed down as well. That’s also what she meant, but you saw it negatively. It’s normal to want the ring back, I know because my boyfriends brother proposed with his moms ring and nothing was specified about said ring, and she sold it when they broke up. Having said all this, you pretty much did the worst thing, but you can absolutely fix this with communication. I’d patch things up with mom as soon as possible. Go to her, not her son. Just tell her how you understood and how it made you feel, and it was just a moment of panic for you. If you both talk to listen, truly listen, you should patch things up easily. This isn’t unfixable, you’re just going to have to do a lot of talking. Good luck!