There’s not much you can do unless you know for a fact that she is being physically abused. You can try calling the authorities from a payphone (do they still exists?)
It’s a very delicate situation. There are also some organizations that can come to help to sex worker in crisis.
If you have serious doubts about someone, please send me a direct message and we will see what can be done.
To start with do your homework and book SP that don’t look like drug addicts.
Legitimate ones do have web sights and photographs.
There is also a place called Merb where there are reviews to check out.
Unless you want to go on a crusade to save all drug addicts, but then why just SP.