If she was attracted to you, I think there would have been some kind of sign within ten sessions. Like, asking if you were single, or making it clear she's single.
Sorry to be cynical but it sounds like she knows what to say to keep you coming back for more, and that's all there is to it.
If you want to find out one way or the other, I suppose either subtly ask if she does extras, or subtly ask if she'd like to go for a drink - depending on whether you're hoping for a wank or a relationship. Prepare for her to take offence at either, unfortunately.
Just out of interest, does she (or her shop/parlour) have any reviews here, or any form for doing extras? Or does she/they have a reputation for being strictly legit?