This advice seems designed to drive the friend deeper into her abusive relationship. Dear Therapist: it is possible to raise concerns about a relationship with a serious power differential (he's her employer!) that's causing physical harm (she's been hospitalized multiple times!) without moralizing about the generic evils of BDSM and non-monogamy.

My advice would be that LW locate BDSM educational workshops in their area and suggest her friend attend--or even offer to attend with her. Help her learn about safer practices. Help her understand that hospitalization is not a normal consequence. And, more, help her see that her Professor Boss is not the be-all, end-all source of kink--because once she realizes that there are multitudes of people who would be interested in engaging in kinky fun with her (fun that doesn't lead to hospitalization), I suspect this relationship's days are numbered.