This is a bad idea. It may seem win-win but it has all the lose- lose makings.
You are exposing part of your life that should be private. Even if you tell her it’s a one time thing, then she will always suspect it. Plus it’s like the old joke “”Does your girl suck good cock? Yes? How do you think she got that way!” How do you think your GF will assume you know this life.
Second, what if you pay a little more attention to the pro? My guess is a little jealousy will go a long way. “Is she prettier? Was she more wild? Does she do things I won’t? Do you like her more?”
Third, what if she likes it too much and the two ignore you. Then in about a month she goes out with “the girls”. What will YOU think.
Want to do a three way? You and 2 pros. Or a one night stand with 2 others you meet in a bar. Emotional attachments by 2/3 In a three way can end a relationship.
Good luck. And hope it works out.