terms具有“条款；条件”的意思.terms on sth.……的条件
terms on which she would be employed 指“她被雇佣的条件”
terms on which she would do 指“她做的事情的条件”,就不符合逻辑了.
if确实可以引导条件状语从句,但不是这样用的.你可以用一个简单的方法来判断if条件句用对没：如果if引导的句子在句首,你把它放到句尾,在句尾就把它放到句首,看意思变不变.比如：
if you have 10000 dollars,what will you do?
What will you do if you have 1000 dollars?
意思一样.但：
if she's employed ,stating the terms on which she would do .意思不对了,是不是?
你的句子里的if是“是否”的意思,是if的另外一种用法.
希望对你有所帮助.