I have talked with many spa girls. What I hear is: it's mostly acting, but its very dependent on the client. The girls I talk to classify about 80-90% of their clients as human driftwood. And some of the better clients want to just be transactional (I was like that for a very long time). But maybe 5-10% of the time there is a genuine connection.
If they see you outside the spa for free, you know its not all acting. Also, if they give you extras (like a BBBJ or BBFS) without expectation for a bigger tip, then its not all acting either. But sometimes they play the long game and are trying to milk you
Many of these girls end up in AMPs after trying other jobs first (restaurant, nail spa, etc.). I also think they enjoy the $$ and some aspects of the job, like being able to nap, watch TV, play stupid apps during the day. It beats standing on your feet all day in a restaurant for less than 25% of what you get at an AMP.
I have no doubt some take pain killers and have long term issues. I know one provider who got out because it was "hurting her body". It was probably the smart move on her part. No doubt others just stay in until they break. Still, I have only heard one explicitly complain about health issues.