Female led relationships discussion

My wife & I are both switches and love it that way, recently a female friend of ours was visiting my wife and she noticed a set of leather cuffs & a paddle on the table, she’s single was married once very friendly and open minded, she asked my wife whats that for and my wife said we like to play games and its sexually exiciting and we both switched roles. She asked more about it and said she would like to be a submissive, but had no idea what it would be like or be a sub to someone she trusted. When I came home from work she told me about her conversation with Michelle and asked my opinion, my suggestion was to have her come over and visit our play room, look around and ask any questions, I would join in if asked. My wife thought that was a good idea and she invited her over for coffee, since I was at work I was left out. Long story short she wants to have a session and try being a sub, her biggest worry is doing something she doesn’t want to do, being forced to do something she doesn’t want and she doesn’t want sexual contact. After she left my wife called me asked what I thought, asked does she want a session with only my wife, with me or both of us. My question is how do we get her interested and moving foward? My suggestion is have the 3 of us sit down and discuss what interests her, her limits etc. My other question is how do we legally protect ourselfves from her saying we forced her to do something.