IT DOES NOT MATTER WHAT-SO-EVER what your wife's company policy is regarding unused vacation. If you are in the US, there is a federal law, called the Golden Bear Rule for the case precedent, that mandates all unused vacation time be treated as if it were wages. It is Federal law that vacation time is accrued pro rata, i.e., they must pay her fractions of days if that is the standard by which they pay her wages. If she is paid monthly, they must calculate her wages to the nearest day, not the nearest month.
If her employer gives her any grief, tell her to file a complaint with the local labor board. I will guarantee that her employer will not need any more than one phone call to their labor attorney to set them straight. I've been there on the employer side. I tried to fight company vacation policy against two ex partners and lost a huge sum to attorney's fees, and had to pay the vacation time on top of it. As I recall, it was even more vacation time than they had initially demanded.
"If you are going to walk on thin ice, you might as well dance!"