You are going to lose by forcing them to leave.... 

You may not find tenants for a few months during which time you will lose up to $5000.  

It's nice just sitting back and collecting interest instead of running around meeting with sellers, contractors, title companies, etc.Yes i found this a very natural progression for many investors.. almost all start out with rentals.. and over the years they just burn out of them.. but want to stay in real estate understand real estate and then morph to the debt side instead of the equity side.. but believe me when a loan goes bad you do have your work cut out for you.. and you can for sure lose money.. 

You don't want to buy a house in the wrong location and not see an appreciation, or worse, lose money.

Don't give the properties to them before your death or they lose the stepped up tax basis.

Simply wait for a deal that is too good to pass up that will cover you if your property loses 10% of its value.

She explained in her email to me that the chance to save money is too hard to pass up and as is willing to lose her deposit if she opts to move out.

Effectively losing one rental but gaining two more (would move out of my current house with ADU and have it 100% rented).A driving factor is how will selling this asset accelerate you to your next goal? 

Are you going thru Your brokerage to conduct the transaction or by way of being an investor are you simply going to the seller, putting the property under contract and closing or double losing with an end buyer and not involving your brokerage?

Also, check minimum lot size and street frontage as you may need to carve the mobile home park out of the existing lot versus pile onto the existing lot, so if you are trying to preserve the existing structure, you may lose some lots considering setback requirements and access.Your local government may require public water and sewer for a new mobile home park, so be sure to check the requirements and distance to the nearest connections.