The burden of proof is on you. You need to prove she didn't work for you, that might not be that easy or worth it in the long run. You have two options.
1) Pay her the liquidation and get her to sign off on it along with the secreteria de trabajo.
2) Lie like a thief and tell them she stole the headed notepaper etc etc.
You might find it's easier to pay the RD$16K and move on. Trust me, it's been a cheap lesson.
Now you know why some employers treat their Dominican employee's like total crap, because many deserve nothing less. Sad but true
