Mom is definitely a prostitute, a high class one but definitely a prostitute (the one aspect of this game that I do not like), providing sexual services in return for money, to the tune of $2000. The services provided by a dominatrix are of a specific type, but definitely of a sexual (fetishistic) nature. She also grabs your penis and lets you kiss her breasts, which are nearly always sexual acts. You can, absolutely, be a dominatrix without being a prostitute, but if you take money for being one then you are also, absolutely, prostituting yourself.
I am also exasperated with the game over that occurs if you reveal yourself during your meeting with her. Mom kicks you out of the house, and prevents you seeing your sisters (when she had just hugged you for helping, or getting on so well with them), claiming you are untrustworthy simply because you discovered her occupation (about which she has presumably lied to her daughters for years). The hypocrite. Because, of course, it is far more trustworthy to get naked and let her hold your dick.