I agree.

If she was a cotenant then her responsibility was to the landlord. She never owed you any rent or deposits.

If you did a sublease then she would owe you, assuming it was a valid sublease.

Regardless, you already know she won't pay and likely doesn't have the means anyway, so there is little use pursuing her over the damages.

The landlord will be coming to both of you about the damages and you seem the most likely to pay.