What do you mean allowed it?
If it's in her name he could not stop her. The police could do nothing. It's either allow the till to be raided slowly on an ongoing basis, try to plead with her to stop, or say I'm leaving.
I can't figure out why he is considering paying her 200k if it's mostly in her name. He says he will borrow the money to pay her off, but the bar won't ever be majority owned by him. Was he going to get another Thai partner to come in to assume the 51% stake? Or, assume she will disappear without taking more money while she remains in control of the business?
If not, what good does it do to pay her off with external money. It's not money the bar had made.