Tenant Dispute & Landlord Responsibilities

Hey BP community, looking for a little advice here.

I have 2 married tenants in one of my duplexes. They are going through a rather messy separation and one tenant has vacated the property but has not retrieved her belongings. I will be having the remaining tenant sign a new lease in the next week, but for now they are both still on the lease. The tenant who is still living in the unit refuses to let the other tenant access to retrieve her belongings.

What are my responsibilities as a landlord given that both of them are still on the lease? Right now I am of the opinion that this is a police matter and that I should tell the tenant living in the unit that if she is unwilling to give her partner access to the unit, that I will have to be present with the police to make sure she allows the other tenant access.

Any advice/resources yall can give would be greatly appreciated.