14 is not too young to have a Saturday job. It’s never too early to learn the value of money and that it doesn’t magically appear, you have to earn it.
About a hundred years ago, when I was 13, I worked in an old fashioned greengrocers for £1.30 an hour, lugging round sacks of potatoes & boxes of apples. I was a girly girl and hated the dirt and “roughing it”, but hey - £1.30 is £1.30! I badly wanted the money (we were a single parent family on benefits, free school meals etc, so I didn’t get pocket money) so I knew I had to work for it.
Could it be that she is “bored” because she’s not allowed to play on her phone whilst working, and is struggling with that?
A younger relative once mentioned wanting “a nice Saturday job”. In my (probably very outdated) opinion, Saturday jobs aren’t supposed to be “nice”, they’re a way of making money. I guess it comes down to how much your DD wants the money. If she’s not bothered about earning money, then she would probably be happy to give up the job. However, there is a chance that she’ll quit, then a couple of weeks later realise she misses the money, but won’t be able to get that job back.
Yes, I know I’m a dinosaur.