Looking to go Italy with girlfriend where do you suggest?

reiteration

it will be very tempting to go to Capri for a day trip but i'd reconsider
very pricey to get there and stupidly busy. having said that i was pushed for time, but the queues for anything are long and everywhere is crowded. if it's between that and something else i'd consider the other thing
if you do one thing in Roma make it the Colosseum. there will be massive queues but is worth it. you can really feel the history in that place