In Little Graduation when Steven brought up being stranded on an island to Shep, Sadie was visibly disturbed. That suggests to me that Sadie has not told Shep of her behavior in Island Adventure. Likely she hasn't told them about events in Joking Victim either or likely anything involving her rather disturbing behavior towards Lars.
If Shep genuinely doesn't know these things will Sadie ever tell them? If she doesn't and Shep finds out through other means will it affect their relationship?