I ask her whether [the brain tumor] helped mark this turning point for her. The answer is yes, but also no. Even before the brain tumor, Giertz says, she was starting to feel like “it was harder and harder to come up with ideas. I was always concerned that it was eventually going to be like beating a dead horse, and that the joke was going to be over and I didn't have anywhere else to go.”

I don't read this being about insecurities but rather more about physical comedy not really being something that comes easily for Giertz, and the stress associated with the brain tumour forcing the early abandonment of that sort of work.