I attempted to provide a review on a provider and was advised she was delisted from TER?  Can I find out what delisting is and why she was delisted?

She got banned or chose to leave for a variety of reasons....

Thank you for the insight.  I have seen her a number of times and still do.  We have never talked about reviews on TER.  
I know some providers request no reviews.

... to ask providers if they WANT a review, if they haven't made it clear they'd like one.  (The exception would be if it's a dangerous or rip-off/bait-and-switch or other situation that you feel you need to warn others about.)

As you said, some providers don't want reviews--perhaps not at that particular time (eg due to school finals) if not at all.  

If you had a good time with her your chances of getting a straight answer from her are "reasonable"  Your chances of getting any kind of reason from TER are ZERO.

 
Providers are delisted for a whole myriad of reasons, some by their own choice, others are kicked off the board for a variety of different transgressions. You already know if she is legit or not by having seen her. I guess it really doesn't matter a lot at this point, does it?