My cousin smoked weed 52-53 days ago. she only did it once. will it show up in a urine test?

No: In the unlikely event that it does, it will be at a low concentration and she can claim that it was passive exposure. This isn't the place to debate the cannabis laws. Best wishes.

Marijuana: Urine drug testing for cannabinoids is widely available and inexpensive. A positive test only establishes past use and cannot be used to diagnose intoxication or a cannabis use disorder. Urine tests for cannabinoids remain positive after discontinuation of cannabis for up to 7 to 10 days in a casual cannabis user, 2 to 4 weeks in a heavy user, and months in a chronic heavy user.