As wiredharpoon said, I would get with the ETL AP to see how they would like to handle this. $2,000 is an incredibly high amount, so not only is she likely engaging in fraudulent activity, she is being highly disruptive to the store's activities by commanding the sole attention of a TM for long periods of time and likely requiring trips to the safe to replenish the cash. I'm sure AP or your store's other leadership (STL, ETL GE) would like to put a stop to it.
I personally wish we would go to Jamba Juice's policy for gift card cash outs in CA- if it's one card and under $5, they'll do it in store. If it's over $5 but under $10, or there are multiple cards, you have to mail them in with your name and address. I'm sure all the fraudsters looking for an easy target have moved on from them...
Have you asked her why she's cashing all of them out or has she offered an explanation? Do you ever see her doing anything else at the store?