First she has dropped you in it, and should be expected to pay at least some of it.
Second the university should have really gone through the consequences of withdrawing with her – if she has actually withdrawn at all or just stopped going? If they didn’t explain then complain.
Third speak to the student accommodation office and make sure they are advertising the room, as you never know someone may have come through clearing and desperately need a room, and some uni’s have students starting in January.
There are usually loads of students that drop out in the first two weeks, as they are home sick, wrong choice etc etc, so there will be empty rooms all over so the chance of actually getting someone is highly unlikely, unless its a new build right next to the campus.
Read the contract, sometimes with medical reasons you can get out of it, but you will need dr’s evidence.
AirBNB it