"Girlfriend Experience" is just a general characterization rather than some specific set of things -- even when one finds a lot of commonality in offerings under that description.

 
The solution is to read the reviews. Those will tell you what others have experienced with a specific provider and you can make you decisions based on that data.

disagree with part of your post. She will not be dissatisfied-she will have your money.
One other thing you can do is after screening ask if her reviews are acurrate  or ask if OK to ask some questions. Do not mention money in any way shape or form.
Even doing this- some will welcome the question other May go dark
If established here could DM her reviewers and maybe get some better answers.

saying that you are looking at a lady NOT reviewed on TER??? There are reviews on a couple of other sites,  but honestly TER is known as the best.

Another thing you could do is look for a lady's website. Sometimes she will have a "Menu" or "Testimonials" which MIGHT help you.

Back before the Pandemic, the general "description" of GFE typically meant:

DFK
BBBJ
Multiple sexual positions using a condom

Now some Providers seem to be changing this a little bit, but, imo most of the mature ladies are still offering these services.

Do you care to share what the actual service is that you are looking for?

MUAH, GT

might get you somewhere.

 
Go onto your local board and tell them what you are looking for.

 
There may be a local provider who will PM you who does what you want, or another hobbyist may know someone who is right up your alley.

 
Best of luck.