The name that appears on the visa is it going to be her maiden name or her married name

The rule is to issue a visa in the name on the passport. I've seen one exception/error.

Did the name legally change at the time of marriage? This is not always automatic. It depends on the jurisdiction in which the marriage took place, generally, but your circumstance (from another thread) is somewhat unique in that the marriage took place in neither party's home country. The third country has no jurisdiction to change either of your names, so I suspect her legal name hasn't changed and you've errantly used a non-legal name on the petition.