How do I resolve disputes among tenants

[RJ Peralta]

Shalom to all.

I did a quarterly inspection to one of my properties yesterday and while I was there, the tenant informed me that the third person on the lease for said property (3 people used to live there but one moved out without taking there name off the lease) comes and goes as she pleases and threatens to call the cops (can legally do so) if not allowed access to the property even though she doesn't live there anymore.

I've dealt with similar situations before by having them sign a lease termination form, since the remaining tenants can more than cover the rent. The problem in this particular scenario is that the tenant in question has personal problems with the other two tenants, is not on speaking terms with them and now refuses to sign any release.

Sorry for the long wording but I really nees to nip this in the bud before it gets any worse.

Any tips guys?