Umm, she's not likely holistic or bilogical then, even if she professes to be. Does she belong to the appropriate associations? Where did you find her? It's always best to sit down with any doctor first and have an initial consultation. I assume you did this? This is to not only get a feel for them, but more importantly, verify the specific protection protocols that are going to be used during the procedure. If she didn't use anything, find someone else. If you've only had a few replaced, you'll be ok, but I'd still look for someone whose going to limit your exposure.
My general dentist (the local one I see for cleanings and checkups) doesn't use Hg either and says all the right things too. However, when I probed about replacing my amalgams, he didn't use any protection elements, so I was forced to look elsewhere for this kind of dental work.