I've heard of people starting at 1mg for several months, then being bumped up to 3 or 5, then higher as necessary.

But it seems to me that there are two issues you're facing: one is whether your dosage is appropriate, and one is whether you are comfortable continuing to see the provider in light of the way she addressed your concerns. I think it's curious that she felt the need to label your doubts. Of course you lack trust--most people with PTSD do. Does she generally respect your concerns, or is this a pattern of behavior? IMO, you should never feel like you can't ask questions or discuss your treatment with your provider.