You need to establish a paper trail that they are their without your consent.In the future, I would highly suggest that when you have tenants move out that you immediately put the utilities in your name with a notification that the billing cannot be changed without your specific consent.  

If they are existing renters, you cannot change the terms of their existing agreement without their consent.

On this Rental Agreement the following:           "Landlord reserves the rights and Tenant agrees to permit and allow Landlord/Owner to market/show the room to              future tenants by giving Tenant notices to show the room on the following day or twenty-four (24) hours in                          advance by text/call and on some exceptions allowing Landlord to market/show Tenant’s room on the same day                of the notice given to Tenant when potential future tenants are pressed for time with or without Tenant’s consent"My question is:  will this hold up in court? 

However, you have to stay overnight on the property/ be generally available and any violations are grounds for revocation of the permit.

I really don't know any details about what had lead to her leaving.As far as I understand, my hands are tied without her written consent.

It may work as an irrevocable, it may be revocable, it may not work at all in your state. 

@Adrian Langdon Maybe I don’t fully grasp the concept, but I’ve never understood how rental arbitrage works given that any landlord with half a brain would put a clause in preventing a sublease without consent.

The biggest issue will be the collapse of the Dollar after this admin. All the trillions the fed will have injected into the economy to keep it afloat will cause massive inflation for the next admin. The New York Fed ...

I think the best course of action would be to get their consent I writing they they not longer have access to that part of the property.

I stumbled across proof-positive undeniable advisory from the authority.Contracts are assignable with the seller's consent.