They both need to be confronted.

You can't honestly be satisfied with a "Oh I don't like to hang up on people so I talked to him for 7 hours" cop-out, can you?

I mean, in 7 hours you have a bazillion opportunities to get off the phone if you truly wanted. "Hey sorry I have to go eat now" "Hey I have some things I have to take care of" "Oh hey we've been talkin for awhile now, I better get off this phone" etc

Your girlfriend isn't as innocent as you'd like to believe in all this.