You are liable for the damage your friends caused so you are right to have paid for them. Obviously you are not criminally responsible. If the police contact you, which is unlikely, just tell them you didn't do it but have paid for it.
Regarding moving out, if you have a contract which your landlord won't budge on, then there is nothing you can do. She can't stop you moving out put you will be liable to pay the rent.
You are obviously not the perfect housemate judging on this incident alone so I would try harder to get on with the other tenants.