It can help to follow exercises to develop your craft. There are books out there, like Fiction Writers Workbook by Novacovich or the red book that goes with the OU undergrad course.
There are also online courses like the Futurelearn one which is free. Marian Keyes did one recently on her Instagram - one lecture a week followed by 5 daily activities. It's all still up there. The writing might not be her style but the principles are transferable.
Or try a local writers group, who she might feel more comfortable developing with. Better than with a bunch of people who don't really get it, or who attack anything that makes them feel inadequate (teens). Sally Rooney did this, starting about 15, in a small village in Ireland. She says herself her work at that age was rubbish, but was very important for her development. She went on later to study literature and film.
I'm less good at online - there's scribophile.
Elizabeth Gilbert (eat pray love) did a creative life podcast where she says if you can't find your tribe you have to build it. She did that to develop herself a supportive group.
But being prepared to write rubbish, and getting constructive feedback are important parts of the process of development, as is critiquing others and understanding why it works or not. Its figuring out where to get that experience.
If she looks at Nanowrimo she might find some links from there to find her tribe online?