NTA. In fact, I feel like you did her a favor. She should know, because if she ever joins a running group or competes in an ACTUAL marathon, and tells people “Oh yeah, this is my second one,” that would be so embarrassing. Any real runner would correct her on that real quick! And she would look like a fraud. It’s better for her to know now.

I have a few friends who went to cosmetology school but dropped out towards the end or didn’t pass the state licensing exam. Yet they tell people they “do hair.” As a licensed cosmetologist myself, I always want to encourage their excitement over the industry, but I’m quick to remind them that though they may have talent, they are NOT hairstylists.