"The Prom Show"

In "The Prom Show," the band for a high school prom that's being held at the restaurant doesn't show up, and the waitresses volunteer to sing instead. Does anyone know if there's a reason why Ann Jillian didn't join in? She has an incredible voice.

At the beginning, they mention that Cassie has a cold, but nothing ever develops out of this in the plot. It's just a random detail. Then, later, Howard accidentally handcuffs Cassie to a pole in the kitchen and can't get them undone. While she's handcuffed, Dot, Amy, and Jan sing "Dancing in the Street." Immediately after the song is over, Cassie is freed, so it seems the only reason that she was handcuffed was to keep her from singing.

I know that Ann Jillian wasn't well during this season and that she was undergoing chemotherapy after her double mastectomy. Perhaps she wasn't feeling well enough to sing. It's also possible that maybe the producers thought it wouldn't be believable for someone with her voice to be waiting tables and not seeking stardom like Dot (who took the lead in the song).

Anyone know? This is super random, but it bothers me. It just seems that the whole episode was centered around keeping Cassie from singing, from the cold to the handcuffs.