My son worked part time at Alton Towers when he was 16 as well as being a steward at a Stoke football ground.
Alton Towers is one of the few employers who don't use the 'youth rate' and pay everyone at least NMW.
Out of my nieces, nephew and teenagers I've know. These were pre covid.
Washing up in pubs, particularly on a Sunday. My cousin did this from age 14.
Various shops including M and S (That was a student and she's tell the class "We don't know which day they are doing a flash sale but I have to be in for 6am tomorrow")
M6 Toll taking money at the toll booths.
Waiting / waitressing - good money if you are prepared to work Christmas day / New Year's Eve.
Caring - harder to get if you don't drive but care homes will sometimes employ teenagers.
Working in a bike shop - was a good customer before being offered a job.
Small local cafes / sandwich shops sometimes have Saturday jobs.
Working in a garden centre.
A lot depends on where you live and if you can give DD a lift to work, places like garden centres are not often on bus routes so there are fewer applicants.
Call centres, depending on her 'telephone voice'.