"I have a gig tomorrow" - What's that mean?
SCRIPT
Gabrielle: "You know, Edie, I'd love to go, but, um, I just got back into modeling, you know, just for fun, and I have a gig tomorrow. I can't leave 'em hanging."

QUESTION
I have a gig tomorrow
= I have an appointment (or schedule) tomorrow.
Am I getting right? or not?
Please tell me your thought. Thank you!

Question

"I have a gig tomorrow" -> What's that mean?
SCRIPT
Gabrielle: "You know, Edie, I'd love to go, but, um, I just got back into modeling, you know, just for fun, and I have a gig tomorrow. I can't leave 'em hanging."

QUESTION
I have a gig tomorrow 
=> I have an appointment (or schedule) tomorrow. 
Am I getting right? or not? 
Please tell me your thought. Thank you!

Answer

In this scenario, gig means JOB. The word gig is commonly used by musicians. When a musician says, "I have a gig tomorrow", it means he has a job tomorrow.

Answer

It means I have a job. She means she got a job modeling, or yes, in other words an appointment, and she has to go. 
"jake and his band got a gig at the new club in their town" this means Jake and his band got a job performing for the new club in town.