keith,
Rail passes are rarely a good deal for Italy, as tickets are generally inexpensive there, especially for Regionale trains. She might find that the cost she's paying per day for Regionale trains exceeds the cost of tickets. One other point to mention is that Passes do not include the compulsory reservation fees for the express trains (Intercity, Freccia). She would have to buy those out-of-pocket. Even with a Rail Pass, if she's caught on an express train without a reservation specific to that train, date and departure time, she'll face hefty fines which will be collected on the spot! I don't believe Passe cover some of the other train lines in Italy such as Italo Treno or others.
The best policy for Italy is to buy Regionale tickets locally, either from a Kiosk or staffed ticket office. She must BE SURE to validate these before boarding the train on the day of travel, or again hefty fines. Travellers can save considerable money with pre-purchase of tickets on the express trains. The Super Economy and Economy tickets are discounted, but these are limited so must be purchased well in advance. Super Economy tickets are non-refundable and non-changeable once purchased. One of the easiest sights for buying tickets on trains all over Europe is www.trainline.eu. Registration is required on the site including payment details but once that's done, it's very user friendly. They also have a smartphone app.
A Rail Pass may be beneficial for other countries in Europe, but without more details that's difficult to say. One important point is that the high speed trains in France (TGV) also have compulsory reservations, which she would have to buy locally. France limits Passholder reservations, so once they're sold out for a specific train, she wouldn't be able to get a reservation even if there were seats available on the train.
You may find this excellent website helpful -https://www.seat61.com/Railpass-and-Eurail-pass-guide.htm and this site https://www.ricksteves.com/travel-tips/transportation/trains/should-i-get-a-rail-pass .
One final point to mention is the three month tiime frame. I assume she's aware of the 90-day Schengen limit (that includes the arrival and departure days). Going over the limit can result in some harsh financial and other penalties!