On the surface, it seems pretty crazy that they would base this division's success on one fight, but at the same time I don't think Zuffa feels that this is much of a risk in the long run. They have to believe that there will be a lot of buys just out of curiosity or just to see the first female UFC fight.
If it draws badly or interest falls off quickly, they'll just cut ties very quickly. I just don't see Zuffa as a company that cares how that will look from a P.R. standpoint at all.