If she is NSW she could call Mothersafe (or interstate equivalents). I had fairly significant amounts of dental work done with DS2, and he is a perfectly well little baby asleep behind me right now. I had the second stage of an implant (cutting the gum back open to reveal the post, doing impressions for the tooth to be made, then having it fitted), as well as filling work on several teeth. I also needed a few xrays. Mothersafe assured me that it was all ok, as did my dentist, and they used to put 2 lead aprons on me just in case.

I remember reading somewhere that you get exposed to more radiation flying in a plane (because you are closer to the sun) than having a dental xray.

Might be worth double-checking that she's been given appropriate abx for a pregnant woman. I also had abx while pregnant. And lots of drugs for morning sickness. As much as I wanted everything to be natural etc etc sometimes your health requires other things.

Hugs to your friend.