The lack of a police report makes me wonder......

Could it have been a fake knockoff of a designer bag where the real item new might retail for $12K? I wonder whether she has a receipt for it. Some homeowner/renter policies or credit cards might help to cover this (assuming that there's a police report as well as a receipt) but AA is likely to say that she should have declared the value and purchased additional insurance when the bag was checked. Opening the bag in such a public place seems to announce what's inside to everyone nearby. If CUN-PHL wasn't nonstop, she shouldn't have locked the bag unless it had a TSA approved lock; I don't know how airports in Mexico deal with needing to open a checked bag to inspect it for airport security and potential customs violations such as drugs. I'm surprised that she's not also complaining about damage to the checked bag or its locks. I wouldn't expect someone to put expensive stuff in a bag from Dollar Tree. A ring would probably be obvious when the bag is X-rayed, but the designer purse wouldn't be apparent that it's anything other than a normal handbag; even upon seeing it most people wouldn't identity it immediately as an expensive designer piece. Depending on where the "merchandise" was acquired, $12,000 worth of stuff might trigger customs reporting requirements too, and when she picked the bag up at PHL she didn't know that the items were not with her. [I'm speculating or thinking aloud here.]

BTW, who leaves the USA with just one credit card? What if an ATM eats it or it otherwise can't be used at your destination? (For example, VISA is most widely used in France, with those issued by French banks being the only ones accepted at some places such as 24/7 gas stations, while in the Netherlands, MasterCard is preferred and can be the only card automatic ticket machines accept.) I wonder how she was planning to get home from the airport or deal with potential overnight delays (meals and especially hotel rooms) or other IROPs.

Is there a Go-Fund-Me account set up to compensate her for whatever?

Anyone near the bag could have stolen her stuff, yet she seems to suspect the AA check in agent (does AA use employees or airport contract workers at CUN?) without quite accusing him of theft. Since she didn't miss her flight after all of the "pay for checked bag and return to counter from TSA checkpoint after twenty minutes to get boarding pass reprinted" routine, I wonder how early she arrived at the airport.

Also BTW, what's the "90 Day Fiance" connection? Was she in Mexico to meet someone she met on the internet who gave her the (engagement?) ring?