You should definetely walk the Freedom Trail, which is a historic trail that takes you to some of the places our founding fathers lived and died. Spend the good part of a day at the Boston Common, a beautiful park in the centre of Boston (The oldest park in the US). And seeing as it is a college tour I would take some time to get her potential neighbourhood. about 6 years ago
Don't know what colleges are on the tour but if you cross the river in to Cambridge to walk through Harvard Yard at the university and you could certainly spend a half day in Harvard Square between the restaurants and shops (home to the World's only Curious George store - that's what the sign says at least).
Rialto is a great dinner spot, albeit expensive and reservations required. Mr. Bartley's Burger Cottage is a famous little lunch spot (cash only). Grafton Street Pub is another good dinner option, not as expensive as Rialto and you wouldn't necessarily need a reservation. about 6 years ago