She also would not likely have been able to cash a $12,000 check the same day, I know my bank has to have at least a day's notice to make large transfers or withdrawals, although maybe they would do $12,000 the same day, but I doubt it. Maybe she deposited it into her account in Austin and cashed out in New York City a few days later. This would have been before the arrest warrant was issued.
International airport travel is limited to $10,000, if I remember correctly, and anything over that amount has to be declared or it can be confiscated by U.S. custom agents if you are trying to take it out of the country or enter the country with over that amount of undeclared money/cash. I don't think there is any such regulation regarding domestic travel, but don't know for sure.