I know of a number of prominent providers that use it.  It she is well-reviewed by established reviewers, has a website, she should be good to go, from what you describe.  The rates kinda make me wonder, esp the overnight rate.  Is $400 for an overnight visit for just a handjob?  I would not bother with an overnight with someone that's only going to give me a handjob happy ending.  

Next question, is the $90 platonic meeting your offer or hers?  Most providers will expect their regular rate, even if it's just for a meet and greet type get-together.  She just does not sound like someone I would be interested it seeing from your accounting of her services, but that's me, not you.

If she has the necessary information for your research, it's up to you.  She does sound legit, I just don't understand the overnight rate.  Can't see spending the night with a provider that's only going to massage me.....

Swim

1) If she is real, she is not offering any extras for that price; there will be a list of upsell charges.
2) If she is real, there is a pretty good chance that you will not get a full hour (or 90 minute) high quality massage; she will try to collect the base fee, then either start upselling right away, or begin rubbing you and then start with the upsell. Either way, if you do not agree to any upsell charges (and they are likely to be high), the rest of the massage will be nothing to write home about if it is completed at all.
3) Overnight for $400? Use your head.

4) What does the text of the reviews suggest?
5) Try PMing the guys with multiple reviews
6) Google the phone number and/or email address, tineye the photos

Other than that, take a chance at the option with the lowest rate - can you afford to piss away $100? If so, book it, take a chance, and if it turns out to be real and good you can always try to extend, or book again.

What area are you in? If you are in a big market area, and she was for real, then she wouldn't have 9 reviews, she'd have 150.

You can't find a one-size-fits-all answer here.  I can only say that BP seems to be a lot harder to find a good provider for escort than other places.

PM the reviewers who have seen her.  Do some research on the reviewers themselves.

Those rates would be consistant with FBSM w/ HJ in my area.   Don't assume more menu than the reviews state.  If she does agree to extras, expect to tip.  In my area FS gals are $$ & up.  I have one Fav lady who starts just this way...  but she expects a generous tip for extras.  I don't consider this an upsell, as no one but a fool would expect a FBSM to give FS for the same price.  $400 for overnight makes me think she is new & hasn't thought this through yet.  A HJ & then go to sleep...  not much of a deal.  
I started with the mentioned FBSM w/ HJ gal & it was a good intro to the hobby.  I'd go for an hour & enjoy.