If you're trying to schedule showings around Airbnb visitors, cleaners, etc. it might be a little more challenging.  

Same lease as everyone else--how many visitors, how many nights a month, etc. 

It is time to evict her.And for those who think this is cruel, I'm one of those "elderly" folks (I'm about to turn 65 in a couple of months and if I get one more notice in the mail about Medicare supplemental insurance I'll scream) and a breast cancer "survivor".Your tenant does have a daughter so she is certainly not alone in the world.  

I could either pay a visit or send a letter.What do you recommend?

I tell him this . "  You are renting the house and the land , you are in charge of who you want to visit or be on the property ( except for me doing maintenance or inspections )  I wont put up signs , but you can , and if someone trespasses you have the right to have them arrested .

I did not get a screaming deal and my rent rate conforms to the market.  

That looks like a screaming good deal to me on the surface. 

@Roshan K. is exactly right - treat the daughter exactly like you would want to be treated - or to drill down even more, threat her exactly the way you would want YOUR daughter treated in the same situation.In addition to the PR hit you'll take if you enforce the guarantee, you'll have to figure out how to keep your own conscience from screaming bloody murder at you in the middle of the night.

You jump on a deal if the number scream to you this is right.

also avoid (or at least patiently, thoroughly screen) anybody who is in a big hurry to rent,   and run away screaming if they offer to pay multiple months up front in cash or they try to get you to to skip any portion of the screening process, or start in on the sob stories.as for finding people with credit better than 700:https://www.fool.com/the-ascent/credit-cards/articles/heres-what-americans-fico-scores-look-like-how-do/so roughly half of people have credit of 700 or better.