"...but Mier stepped down because the Ultra-Right had a hissy-fit because she wasn't conservative enough

Not even close. The "ultra-right", as generally discussed here -- including the religious right -- was for the Miers nomination.

Who was claiming that she wasn't conservative enough?

George Will, Bill Kristol and their ilk were not claiming that she wasn't "conservative enough". They were saying that she wasn't "qualified enough". Of course, George Will, Bill Kristol and their ilk aren't "ultra-right".