So I guess you're referring to the event "Take Lexi out on a date to go dancing Saturday night." in the "Slave Lexi" story.
I went through the whole story and made sure I had the same relevant stats you described (Lexi: LP 90%, KP 100% - Sasha: LP 100%, KP 100%)
I took Lexi to a date on Saturday, ending at the club and the event triggered correctly.
The only thing that can prevent the event to trigger is if Sasha went mad when she met Lexi at the mall (Lexi_meets_Sasha )
Did you collar Sasha before the event at the mall?