... I would pay a deposit to a provider I've never seen before. Too much shit can happen before that appointment ever happens. I would probably do it with one I had seen numerous times before with no issues ... but unless I was paying her to travel to my town specifically, I can't see a reason it would be necessary.
Someone mentioned she has more to lose then you. No, not really. There are plenty of potential clients out there who don't use TER, plenty who do but don't read the forums, and plenty who would read your story and not care.
At the end of day though, you should do whatever makes you comfortable. I will say that if she travels to your area frequently, why not catch her next time when you have more references.