If NYC is within your range my recommendation would be Ms. Marwood http://www.msmarwood.com/overview. About 7 years ago I went into a phase where most of my sessions were "pure spanking" (OK some of those had a bondage element) I was fortunate to discover Ms. Marwood. We did many sessions that were "pretend" discipline at a pretty high intensity but there were a few where I felt I had genuinely done something that warranted serious punishment and she would do what was necessary.

I am sure she would be very happy to conduct your session. I know she does spanking tutorials with couples. She also had a woman who would serve as a witness which is in the same ballpark as the dynamic you describe. I do not think she charges couples extra but am not 100% sure. I do believe that she has gone to requiring a deposit on all first time sessions.

Drawing blood is something of a soft limit with her. She would prefer no bleeding but it is not a hard limit. If your friend thinks she might want to see you bleed a little she should spell that out to Ms. Marwood.

The last few years my interest in "pure spanking" sessions has waned and they are now the exception not the rule. Though I did have one of the "for cause" sessions with her back in May and she was as sharp as ever.