Annnnd now I think my first VRBO guest is a scammer

[Leigh Ann Smith]

So, this woman paid $573 in advance and she owes another $573 on the day of check-in, which is today.  Yesterday she messaged and asked if she could check in early.  She's from out of town and is working nights at a hospital on a contract.   She was going to come at 10 and go to sleep before going back in tonight.  I said yes.  

She showed up at 10 a.m. and the 2nd payment wasn't in yet.  I showed her around and said that I hadn't received the 2nd payment.  She said, "Oh, it'll just take a couple of clicks on my phone to send it."  I said great, and went on back home.  Yes, that was mistake #1.  Then I started figuring out this mess about VRBO holding our funds and noticed she still hadn't made the 2nd payment. 

I gave her time to get her sleep in then went back over late this afternoon.  I told her about the VRBO payment problems, still not really suspecting any problem with her.  I told her I had just sent her a 2nd payment request through VRBO.  She picked up her phone and said okay, she'd take care of it.  She also told me that after she gets off work in the morning, she's off for a couple of days, so she's driving home.  You guessed it - she still hasn't made the 2nd payment.  So, I'm suspecting she doesn't have any intention of paying it....not today, in any case.

I'm thinking I need to text her and tell her that if she hasn't made the payment by the time she leaves tonight (about 10:30 p.m.), then she needs to take her things with her and I'll send a cancellation through VRBO.  I hate to come off as threatening like that and potentially lose a 2 month reservation, but.....

Any suggestions on how to handle it?