There's no way to change the name to a different person.

If your mom isn't going to go then I would just cancel and re-deposit the miles. The first random date in November I clicked on searching LHR-DFW has sAAver business availability on the AA nonstop at 57.5k (and tons of connecting options), so I don't think this award space is quite the unicorn you're making it out to be, especially given the current environment.