Was that her actual project?
She probably couldn’t figure out the potato clock.
Probably the tried and true volcano with baking soda and vinegar.
From the parent article (it is a good project for that level):
As a science student at Yorktown High School, Alexandria tested the effect of various antioxidants on the lifespan of roundworms, known as Caenorhabditis elegans.
When organisms are under oxidative stress, there are more free radicals (chemicals with unpaired electrons) than antioxidants in the body to neutralize them. Those free radicals react quickly with many other chemicals, and without antioxidants to neutralize them, create cellular chaos. Such an unstable cellular environment has been hypothesized to be responsible for wrinkles, neurological diseases and even cancer.
Alexandria chose compounds with the highest cited number of antioxidant capabilities and observed how they impacted longevity of the roundworms. In some cases, lifespan was prolonged for as many as 33 days, almost doubling the nematode’s normal lifespan. Her findings indicated that antioxidants could potentially help prevent degenerative illnesses induced by oxidative stress.