What did Jess suggest to do about the person crying in the bathroom?

The person crying in the bathroom is Janice Avery.  Jess and Leslie believe that they are the cause of her crying.  
Janice Avery is a bully.  She physically beats people up and steals things from them.  Leslie and Aaron come up with a revenge plan that involves really embarrassing Janice.  The plan works, and Leslie and Jess now believe that their prank is the reason that Janice is crying.  Jess feels guilty and suggests that he and/or Leslie should talk to Janice.  Conveniently for Jess, Janice is in the girls' bathroom.  He tells Leslie that she needs to go talk to Janice. 

"Leslie, I swear - I'd go in there if I could." He really thought he would, too. "You ain't scared of her, are you, Leslie?" He didn't mean it in a daring way, he was just dumbfounded by the idea of Leslie being scared.

The goal is to find out why Janice is crying and maybe offer some comforting words of advice.  Leslie is successful in both goals.  Janice is crying because her two best friends told everybody what a deadbeat father Janice has (which is true), and Janice is embarrassed that everybody knows it.  Leslie then gives Janice advice about how to quickly end all of the gossip.  

"I told her just to pretend she didn't know what on earth Wilma and Bobby Sue had said or where they had got such a crazy story and everybody would forget about it in a week."