Here's a chicks POV, and in the age range of the fiancée...RUN.
The threats to harm herself - AND then blame you? And at 42...i couldn't ever imagine behaving that way. Straight up. It's either alarmingly childish or its deeply vindictive and selfish (and bananas). either way for a 42 yr old, that ain't good. And my husband drives me nuts at times. Trust.
Marriage is a long road. It doesn't get any easier as the years roll. So if you're gonna do it get a good one. Because she's showing you her cards. And I agree that it will repeat, perhaps the same or some other version.
i just heard this phrase today from Maya Angelou "when people show you who they are, believe them the first time." I'm sorry dc28...shitty as you obviously had something deep enough for $$ on a ring, but the universe is speaking to you. I don't have all the details but the kind of behavior is no bueno under any circumstances. Good luck.