I think a 2.5L Boxster is honestly the perfect car to get your feet wet on the track. It's definitely not the fastest thing out there, but it's fast enough to get a feel for high speed driving and forces you to learn to be a good driver if you want to keep up with others out on the track - how to brake, learn the line, carry momentum and corner effectively. All of these things are slightly less important if someone's driving a high horsepower car and can simply stomp on it in the straights to crush the Boxsters of the world out there on the track even if they're slower in the corners.
My first track experience was a '99 Boxster, and kept tracking it for 7 years, racking up more and more seat time, improving driving skills until I finally moved up to a 911 this year. And honestly, I'm pretty sure there were still several seconds of improvement in my laptimes I could still shave off in the Boxster if I were to keep tracking that.
Overall, there's a lot to be said for driving a "slow" car fast.
As far as your list, I the only thing I would add is a proper track alignment. I know the stock suspension doesn't allow for a ton of camber, but if nothing has been done with it or it's been neglected, a proper track alignment can go a long way. On the tire question, I have been extremely happy with the Hankook Ventus R-S4, and the price is definitely right. (You have a lot more options on tires if you use 225/45R17 front tire sizes instead of the stock 205/50).
Either way, no need to upgrade stock calipers - just make sure you've got a decent set of track pads and fresh, high-temp fluid like Ate Typ 200. You might want to consider adding larger, GT3 brake ducts and tying up the brake wear sensors so they don't melt from the heat those brakes are going to generate on track.
Other than that, I hope she has fun! It's going to be a blast.
