Ask HN: How to unblock Yahoo email address of recently-widowed grandmother?

My grandmother has just phoned me in some distress. She has just been locked out of the Yahoo email address that she shared with her recently-deceased husband for a decade. Apparently, she had unthinkingly filled out some account-related request for information with her real name, which got it locked as it was her husband's account originally.

She is a lady of resource and mental fortitude, and has already managed to get hold of customer support on the phone twice. However, she's been told that there's nothing that can be done.

My question is - what can be done now? I've already recommended she starts again with another provider, and have promised to attempt account recovery (although I doubt it's possible through conventional means).