confessions of a new doc

so i started seeing this patient about 6 months ago. she's in her early twenties and super polite. always comes to appointments on time with all the necessary info. we hit it off really well, kinda like an older sibling younger sister dynamic. one day when im alone in my office and shes here for a check up i notice she looks nervous. so i ask what's going on and after some hesitation she tells me about how her boyfriend has been pushing boundaries with bdsm play. wants to do more but hes worried shes not ready. i thought it was odd talking about this w me as her doc but i listened. the next week he asked if we could come back for a session where id be there to supervise some of their stuff. honestly i felt weird but also intrigued, and kinda flattered. so i said yes. when they came in she seemed really relieved to have my support. i stood behind them as he led her into some age play scenarios. i watched him put on the role of a strict father figure with her playing the daughter. it was intense seeing them interact this way and hearing her take orders like shes younger than me. i had this weird feeling in my gut, something stirring inside. after their session ended she thanked me profusely, said they felt better knowing there's support from someone professional. i told her i would continue to be a resource but reminded that therapy sessions were another place for discussions of this nature. as shes leaving with him she looks back at me like im the only one who understands. after seeing them off my mind keeps going back to that moment, wondering if there was more i could have done or said. still not sure what it all means and would love to hear others thoughts on this