I'll try to pass along some advice as someone who was just through Venice and Florence this month and Rome a couple years back -- checking out Juve merchandise along the way...
Venice has minimal options -- so don't plan on getting much here. Venetians, despite AS Venezia, is an Italian anomaly as far as calcio tifosi go. There's a quasi-Kappa store on the Rialto bridge that's small and weak on selection beyond bags, jerseys, and smaller items like keychains and discounted "fanny" packs. There's a similar sporting store with a slightly weaker selection depth, but better breadth, at the Campo Manin area of San Marco. Plus the occasional lame flag and 6-year-old size Nedved jersey at tacky tourist stands here and there. Pass.
Florence is a step better than Venice, but it's pretty marginal still (IMO) when compared to Milan, etc. Despite the lot of their Fiorentina merchandise, they seem like a town still in Cecchi Gori denial while losing their fanaticism for calcio (let alone Serie A) at the same time. General calcio swag (no personal reference intended) is pretty limited in areas like the market booths near Piazza di San Lorenzo. I stepped in a couple of sporting stores, but nothing to write home about. Still, I spent limited time here this month -- so you may find things I didn't.
Your/her best bet is probably Rome. Ignore the couple of AS Roma stores near the center for a moment, and there seems to be a much stronger interest in general Serie A team stuff ... not to mention a greater variety of places and offerings. I don't know of any sporting stores offhand, but the options are there and plentiful. Roma is a big calcio town.
(Of course, I could be slightly biased, since the last time I was there was the week after the 05-05-2002 infamy -- and all the stores were still selling Roma championship swag when Juve fans roamed the streets giddy about Lazio's undoing of Inter. :dielaugh: It's always somebody...)
But dang -- you can't beat the Juvestore on Via Garibaldi in Torino, though. It's like a giant bug lamp for juventini such as ourselves.
