Adelaide Miller is Gennice in The Understudy (Season 6 Episode 23).
Gennice is an up-and-coming actress serving as Bette Midler's understudy in "Rochelle Rochelle".
As Jerry starts dating her, he notices she is easily driven to tears at the most minor inconveniences (like dropping a hot dog on the floor). Ultimately, it's too much for Jerry to take, and the two break up.