Hello there,
Unfortunately you agreed at the time to have the refund directly deposited into her account, and the IRS will not stop the direct deposit, as you have found out. You will not be able to access her personal bank account, even if you are her spouse.
Your only option is to pursue this at a legal "local" level, such as using it as an issue or item of negotiation in divorce court.
Enrolled Agent
10+ years tax preparation and tax advice.