It was stable on the Barzan side more than long enough for a sneaky Ferengi to get through.
She had no real prospects of making a decent living without getting caught eventually in the Alpha quadrant.
Constantly having to look over her shoulder and worrying about someone she traded with turning her in for a profit.
Perhaps she felt that her odds would increase significantly enough to justify taking the risk.
Arridor and Kol got through the wormhole originally when they tried bargaining for it... it was their expeditionary mission to ascertain whether the wormhole was stable or not (the ENT-D shuttle with Geordi and Data did the same - only difference is, Geordi and Data got out of there after discernign the exit point of the wormhole was unstable seeing how it was where it wasn't supposed to be).
Once they discovered the wormhole was worthless because it was unstable, the information was quickly disseminated and even the Ferengi withdrew from those negotiations.
But as I said, the Barzan wormhole's AQ end destabilized when Arridor and Kol used a subspace signal to disrupt VOY's tractor beam.
That happened 7 years after the Barzan Wormhole was first seen in TNG, and Ferengi females weren't exactly allowed to leave Ferenginar.
Would Nandi have had the opportunity to leave Ferenginar even covertly and get her hands on a D'kora class starship in the process?
The other female who fled Ferenginar in secret and got lobe extensions (the one who fell in love with Quark) had to do all kinds of things in secret and not draw attention to herself (while pretending to be male).
It seems more like Nandi would have had better chance of leaving Ferenginar and getting her hands on a D'Kora class starship sometime during Ds9 events and flying through the Bajoran Wormhole to the Gamma Quadrant and eventually getting to the Delta Quadrant near the Gamma border.
Otherwise, if that D'Kora class ship had a crew originally and indeed went through the Barzan Wormhole, they were idiots in that case... and I don't think they would have risked going through that wormhole not knowing where they would end up.