Sonia
Sonia is Gloria’s somewhat lunatic sister. Unlike Gloria, Sonia stayed in Colombia to take care of their mother. She comes off as mousy, quiet, withdrawn, but not unpleasant in any way. However, that comes to an end when she discovers what could have been.
We learn later on that when Jay approached Gloria at the diner, he actually had his eyes on Sonia. When she learns this, she tries to seduce Jay on his anniversary. Gloria initially didn’t believe him, but when she discovers the truth, they get into a catfight on top of Jay, much to his delight and satisfaction.