Andrew, why do you think she's back with the OM? Bc of the FB friendship thing?
Also, I would explain why you think paying off debt is better. Show her the interest you would earn in a savings acct vs the interest on your debt. Then ask why she prefers to save. I think it's fine to ask if she's saving for a L. Just avoid painful R talks at this point.
You're doing so well, so keep it up. I know you love her and want to save your M, so feel good about yourself for doing everything you're doing.