I understand you. Maybe that's my mistake. From the outside it looks like what you described, but that's not what I meant. The MC's support of Jacqueline's lifestyle makes Kate think not about sleeping around, but about rethinking her approach to relationships. Something like:
Kate, look at the prostitutes, they love what they do. Kate, look at these people in orgies, they love what they do. Kate, look at these nudists, they're having fun. Kate, did you ever think you needed to be a little more liberated.
By telling Kate that you like Jacqueline's lifestyle, you make her wonder - what if I try to get close to someone else, because the MC doesn't mind. That thought alone won't lead to anything. Then you add. - Would you, Kate, agree to sleep with another girl? And Kate wonders, -what if I had sex with another girl, would I like it?
And all you have to do is nudge her in the direction you want her to go.
You're right, consequence and cause are very different, and I will work on what I write.