This kind of damage can be hard to resolve. But it is commissive waste on the property. Most leases cover commissive waste as a reason for termination of the lease. In this case, it was done by an acquaintance, guest or invitee of Yvette’s. But it was probably not done by her, rather to her.
Yvette has remedies. She will be responsible for the cost of the cleanup. She should report this event to the police immediately, who can investigate further. She can get a restraining order against the person responsible so they cannot return to retaliate or do further damage. And if the statement is true, and the sister is under age, it may also be a crime.
The landlord or owner has remedies as well. Issue a notice to comply. In that notice explain that any further damage will result in termination of the lease and all fees associated with that event. Order the cleanup to be done by a professional so that further damage is not done. Charge the security deposit for the cost of removal plus administration time. As a landlord, Yvette’s personal and family problems are not the business or problem of the landlord. Protecting the property is the business and problem of the landlord. In most cases, the police will handle this issue without any input from the landlord except to acknowledge the damage. Do cooperate with any police department requests. Be sure to get a copy of the police report for the tenant file.