I would love an honest answer

I have always had very stong opionions on when it comes to women comprimising themselves sexually for money. My opinion has always been, do it if you want to, DONT and most definately , dont do it for money! And the secondary question is the relationship that my partner has with his sister . Already sounds complicated hey! The storey goes like this. My Partner and his sister are very close, she is unhappy in her marriage , so  this night ,she is having a bucks night ( pre marraige celebrations for the nearly newly wed) at her home for her sons friend. She rings my partner up and invites him. Telling him < oh gosh you should come over and keep me company (mind you im not invited), and also mind you not her husband to keep her company)saying  you should see the girls here, hot blonde and naked , lots of them around age 19 / 20(Fact here My partner and my self are nearly 50) these girls are about 19ishWhy would his sister be asking him to do this?? He did not attend his choice, as l did not voice my opinion at all!!!  I only give opinions when asked for, or keep them to myself. The next day when we went to visit them, she (age 50) was saying to my partner, wow why didnt you come over, your should have seen it, they were hot. Dont mean to be rude here, she also said they were putting dildos, yah where they fit and was saying it was good clean fun I  couldnt help but voice my opinion and said well i tyhought it was discusting!!!! and asked her , well for $33 per hour, what would she think if it was her daughter.  adn then would it b e good clean fun, and why would she encourage her son to disrespect these women with no common sense. and then WELL INVITE MY PARTNER, I COULD HAVE KILLED HER,  for want of a better word.  Well that got a silent answer... Is this good clean fun NO the girl/woman has no respect for herself and just wants the money , poor sad girl. , but i dont understand why yoy would be tellling your ow sone, this is, alright.. No its not alright.. is this just me??? Why for gods sake did she want my partner to attend..WTF!! Im totally confused here, of why she wanted him to be there. PS my partner and l are very much in love, and have a great sex life, nothing lacking anywhere. I just wonder why she would justify come and watch some cheap slut with me at my home I need a real opinion, please Is this myh insecutiry, or what is this