Sorry to read about the issue.

If the funds were in a taxable account, not an IRA/retirement, you may be able to flow the funds into the trust, then set it up as a payment to her with a 1099 to her for the full amount. Most living trust recognized income flows through to the beneficiary without a return required, you may want to file a return for the trust. Get an EIN for the trust now, just in case, easy to do on the irs website.

If they are in a retirement account, not sure why if it's a trust, then the layers of fuckery get deeper.

Last resort, if the investment company doesn't get it straightened out. The issue there is the company, does she have any named accounts with them? No account, no standing... you are the point of contact regardless of the court decree. File your return and include statement of facts why you didn't include the amount in your return. Attach a copy of the decree, her 1099 for full amount from you and make sure to mail 1099 prior to the deadlines.

Might be smart to get a notarized statement from her that she will get a 1099 for the full amount.

Taxes can be a mess and I absolutely understand your desire to not take on an additional liability that isn't your responsibility.

Get a couple of free consultations with CPAs in the area and ask about these thing and ways you can avoid the liability. I think the 1099 route may be the easiest with the court decree as the driving force.