This is a good time to make sure she knows the rules and guidelines around tyres.
For me that would include ...
ideally replace both tyres on axle not one.
if replacing one, make sure the pattern tread matches the one on the other side (ideally same tyre make and model).
Reasons why part worn tyres are not a good choice (including the stats on the % of unroadworthy tyres sold as part worn)
The benefits of buying quality tyres and how to identify good quality tyres
The alphabet system (don't know the official name) for checking a tyre for its performance, particularly in wet weather (I'm never bothered about the decibels part personally).
Wheel balancing as part of tyre fitting, and possibly tracking as well depending on how the tyre was damaged/car performance.
There's a lot of information online about things to consider.
She's a young driver, I'd be wanting the best possible tyres personally - better grip, better braking, less risk of aquaplaning etc. I'd be more than happy to pay for that.