I agree with Ray. She certainly doesn't need long-term growth. If she makes it another 10 years, she's well above average. Not trying to be a downer, just being realistic.

There are tax considerations, but I would consider moving most of it to CDs. Ladder them every few months. It's very safe, provides predictable access to funds, and doesn't have a 30 year time horizon (which would make her the longest-lived human ever if she saw that to maturity). And it's easy to manage.

The late husband probably invested like he always invested, even when he didn't need to "get more rich" anymore. I suspect I might do the same thing. I'm comfortable with my style, and would not likely change it much. I have a larger cash cushion than normal since I retired, but I still own the same equities (LTBH). Changing my style would involve taxable events that I'm trying to avoid (though some of those wouldn't be relevant to a nonagenarian, like ACA tax credits).

Without knowing specific details, my general thoughts would be to keep a large-ish cash cushion to cover unexpected immediate events, and ladder a bunch of CDs to provide predictable access to additional funds when needed (and if not needed, renew the maturing CD).

And, if she's able, spend some money on herself. Take a trip. Whatever. I encouraged my mom to do that, but she really didn't. And then the dementia set it, and it was too late. I didn't need the money she left me, and would rather she have used to for herself while she could.