Dear WD-50,
I must be dense, because I have no idea what "Goomah" issues signify. Having said that, I don't think we should conflate a "non-pro" massage therapist, Russian or not, with the reviewed professionals that you could contract with through our esteemed website. Of course she could be lying [through her teeth among other places, pun intended], but not according to your calculations. So let's just go with your impressions of amateur hours. Ergo:
This is a very unpleasant and sticky situation. Upon YOUR own initiative, YOU decided to furnish her with extra money, which she apparently felt was a great idea. Now that she's got the hang of it, she wants more. And on top of it, apparently she wants YOU. Trust me, a consummate professional with tons of reviews and a sizeable fan base would never even DREAM of having such fuzzy boundaries. But here you are with some trepidations, and rightly so.
My suggestion to you is to CUT OFF CONTACT IMMEDIATELY. Period. NO ifs or buts, no matter how sexy and ravishing [also pun.] Don't take her calls, don't acknowledge her, nothing. If she starts threatening you, go to the police and contact an attorney for a restraining order. I don't know how you found this "massage therapist" initially, but rest assured that you could screw it up for her royally if you contacted her licensing board and told them that she offered you "extra services." There would be an investigation and while she wouldn't exactly land in jail, they would either put her on probation or simply yank her license. The mere thought for a licensed professional to go through all that is enough to refrain from doing something so stupid as to contacting your SO or whatever else you may fear.
If she gets you on the phone and starts threatening you, then you should simply inform her of your intentions to report her to the board. And then don't chicken out, but do it. Calmly and assuredly.
AND NEXT TIME, FOR GOD'S SAKE, DON'T GO ANYWHERE ELSE BUT TO TER (or your SO) IF YOU WANT TO GET LAID. I don't care what she is or who she is - the fact is that you violated the Holy Grail of Boundaries, which propagates consorting with professionals who do this for a living and who don't shit where they eat, quite frankly.
Now cut her out of your life ASAP, please,
The Love Goddess
...so reporting her to the licensing board won't do much good.
It sounds as if she has come to rely on the additional income you provide; by tapering off your visits, you may have put her in financial difficulties.
You have to tell her she can't rely on you in the future. If all else fails -- lie! For example, tell her you're having medical issues which have left you unable to perform sexually.
Why does she know so much about you personally? Did you cultivate a relationship?