Efheny stayed because ab-Tzenketh is such a remarkable world in every single way, especially compared to Cardassia. There's practically unlimited resources there.
Rhetorical generalities with little substance.
'practically unlimited resources'? Not for her - not for most Tzenkethi. She - they - are slaves. Most, perhaps, willing slaves - due to their genetic make-up and brain-wash. That's the limit of their lives.
'every single way'? Obviously not. If you're talking about positives, that is.
To her it was a place with great resources. She kept remarking how lovely it was to have water, where it's (understandably) limited on Cardassia. She fell in love with the world and that's why she chose to stay. In her mind it's a lot better than Cardassia.