How do I get over the fact that my bridesmaid tried on my engagement ring?

I didn't even realize she had it around her finger until she exclaimed, "Hey! We have exactly the same ring size."

I froze. I had just burned my hand on the stove, and I'd taken the ring off to rinse my palm under cold water. She plucked it from the counter and put it on. This woman does stupid sh*t sometimes, but this one tops the list.

I've had that ring for exactly three weeks. Technically, not even a full three weeks - I had to return it to the shop twice to get it resized and appraised. It has my fiancé's great grandmother's diamond in it.

If only she'd asked before she put it on. I would have told her "no" oh-so gently. Nobody has worn that ring besides me, and I'm selfish. It's mine and only mine, just like the man I'm going to marry next year.

She pulled it from her finger and gave it back to me, then said, "Try on my ring! A friend gave it to me."

I numbly slipped her ring over my finger. I know that she sees both the same. They're just rings to her. So it's hard to blame her. But my insides were boiling just as hot as the burn across my palm.

I left quickly after that and drove home in the dark, slapping the wheel and trying to keep my tears at bay. I'm frustrated with how thoughtless she was.

Isn't it a societal norm that you don't try on another person's engagement ring? How can I get over this and put on a smile while she's standing beside me at the altar?

Maybe I'll just elope.