Email From: field has prefix name with (null)

I have a friend who I help with her Mac and she just emailed me to let me know that people are complaining that in the From:  field of her emails her name is now showing her email address prefix name with “(null)” added to it. 

For instance, say her name is Jane Doe and her email address is janedoe2@example.com.  Instead of Jane Doe<janedoe2@example.com> showing in the From:  field   "janedoe2(null)"  is shown.

Everything looks good on my Mac, however, when I remove her from my Contacts app I get the same thing in the From: field as the others are getting —>   janedoe2(null)

What is going on here?  Do the recipients of her emails have to add her to their contacts, like I do, or is her name missing from her Mac somewhere in order to associate her name with her email address?

It seems this all started when I helped her setup a new M1 MacBook Air for her a couple of months ago. She is an extremely simple user using only the Mail app and Safari. She doesn't even use her Apple ID on the Mac , or have any contacts in her Contacts app.

Any help with what is causing the (null) thing would be much appreciated.