What would happen to Galadriel if Sauron triumphed?

[Voralphion]

The forces of Dol Guldor were held off by more than the power of Nenya, there also were the soldiers led by Celeborn. Sauron regaining the ring would have had little effect immediately as he didn't have any of the Nazgul there, being the only ones of his servents that would have had an increase in their power. I think they could have held off the forces of Dol Guldor enough to be able to retreat safely and leave ME.

According to Sauron's previous conduct with the previous ring bearers he had captured (the dwarf with the ring, and the Nazgul) would he enslave her?

No he wouldn't have been able to enslave her but he could know her thoughts and undo all done with the ring. No dwarf was enslaved by the ring. The rings had no effect on them.