How to turn down my neighbor with no hard feelings?

Wasn’t sure how to word this question… A neighbor of mine is teaching an improv comedy class. She’s been talking it up trying to get people to register, and basically expects everyone she’s talked to to sign up.

I’ve done my fair share of improv comedy, and I really hate doing it. If it was free, I’d go to support her. As it is, I’m sure as hell not paying a bunch of money to do something I don’t want to do.

The teacher knows that I make my own schedule so being “busy” on that night will be tricky. I’d rather not lie. What can I tell her to not hurt her feelings? She’s convinced that her class is embarrassment-free so she won’t accept that excuse.

Thanks!