Regardless, we are BOTH signing the lease. He is responsible for 12 months, as am I. So in a distant reality where the Boston housing market isn't a nightmare and she up and decides "Me or her!" and he has the money to pay to break the lease... it would be very much his problem/the problem for the property managers.
Zach talked to the leasing office, and they told him too bad--both of you are responsible for 100% of the lease if the other bails. They don't care who pays the rent, only that it is paid.
He even talked to a lawyer about small claims court. Lawyer said don't bother, there was nothing that could be done. Zach ended up having to find a last second roommate on craigslist to pay the rent.