Legal Question in Landlord & Tenant Law in Kentucky

Probably nothing. Likely the girls signed as co-leasors and are both on the hook for paying the rent on time, and the landlord can't accept payment from only one of them. If the roommate doesn't pay at all, your daughter will have to pay on her behalf or face late fees, penalties and eviction. She can recover unpaid rent by suing her roommate in small claims, but if it's a matter of she just keeps being a few days late and your daughter has to cover her in the meantime, there's really no recourse. I would suggest she have a blunt conversation with the roommate that makes it clear she cannot cover her rent, even for an extra day. And find a more reliable roommate when the lease is up.