... depending on the locale.  Some states define prostitution as offering or agreeing to exchange sexual favors for money, or agreeing or offering to exchange money for sexual favors.  And "sexual favors" can include any form of sexual penetration or contact that is done for the purpose of satisfying a person’s sexual impulses.  

A potentially bigger issue for the masseuse is losing her massage license.  In most states (maybe all?), there's laws regarding what a massage therapist can and can't do.  Sucking on your boobs would probably be outside those laws.    Even massaging you without draping could be enough of a violation to lose licensure.  

If you're caught, of course.