We rarely discuss finances because it’s frequently a source of tension in the relationship.

Good lord, what were you thinking? It's fine to keep finances separate if you're not married. And it's still fine to keep it separate even after marriage, depending on what works for you guys. But you need to be able to talk about finances openly and honestly. How can you expect to live a harmonious lifestyle together if you can't? At minimum, you need to call off the engagement. You cannot actually believe this is a good set-up for a long-lasting marriage. Also it's her responsibility so no, YOU don't need to bail her out. SHE needs to bail herself out. SHE has to come up with a plan and show it to you and then enact upon it to prove she's serious. If you so insist on staying with her, you should not get re-engaged until and unless she pays ALL of this off.