If you contact a lady through P411 and her page says she offers a discount, do you assume that's what you should pay? Or do you ask? Let's say you see her more than once. Do you assume you go on paying the discounted rate, or do you ask each time?

And as long as she offers the P 411 discount that is what he should expect to pay, if she stops posting the discount, I would suggest you ask her what is the proper "current' donation. You don't have to worry so much about "discussing money" at that point as you are proven customer.

Yes, and it usually will specify whether it's the first or next session.

It will probably remain the same unless it was a one time thing for her

The first time I used it I double-checked with the provider to make sure about the discount. Now when a provider has it on her page and that's where I contact her, I expect it to be current info and don't bother asking.