This is the hard part of writing comedy: not knowing a person's delivery style, or, for that matter, the person, the target audience, and, importantly, the person's age. Am I writing for a 14 year old girl or a 24 year old girl. Big difference. Is the audience a church group or a nightclub crowd. That makes a big difference. Notice how I bracketed the insult part of the addition to the joke you gave? Church crowd, the insult could go anywhere from dweeb to dumb broad. The nightclub circuit would start at broad and go to any other form of obscene insult. Bitch would be the most common, but considering today's lack of manners, the insult could be a slang name for a body part, especially parts Germaine to her gender. I could spell it out further, but I don't want this to get outright obscene.
An intro into jokes? Remembering me saying talk about what you know? Add onto that, find topics that an audience can relate with.
"We've all gone to the movies, right? A walk in theater, not one of those drive ins where half the county's population was conceived, but a REAL theater.". At this point, be prepared for the heckler to yell out that they've never been to a theater. While there is some reparte that could go here, I'll hold off on that. Just start over, with a twist. " Everyone THAT HAS A LIFE has been to the movies, right?" Make sure when you yell that one part out, you glare directly AT the heckler.
Now segue into the theater jokes.
I almost hate going to the movies. People are so rude! Take the chatterboxes, for example. Your trying to get into the film and some oaf is behind you talking a mile a minute, drowning out the Dolby Surroundsound system that the bowling alley complains about being too loud. You know the type. Yatchata Yatchata Yatchata (use hand here to show mouth movement of offender) I got mad one time, turned around and said, 'Excuse me. But I can't hear a thing!' The girl looks at me and says. I hope not! This is a private conversation!' Then she called me a nosy bitch.
Then another time...
And here she can go into other theater jokes. If she still has time, she can segue into discussing movies and actors. Give it about a five minute time limit. A perfect YouTube segment. Practice practice practice.
Importantly, though, is have her take a public speaking course. She has to feel somewhat comfortable talking in front of people because she needs to get a good idea of timing. Getting a venue is never a problem. We'll discuss later.