John, MikeK, Mountainside:

Thanks for responding.

Yes, a backup would have been very wise, obviously something she now deeply regrets.

I don't know why Mountainside's Download folder is intact while my wife's was cleared.

The Microsoft support person wasn't very clear on how the update decides to remove third party software.
I'll look more into that.

GChinCH:

Thanks for finding the articles mentioning that some things are sometimes removed in the Windows 10 update.

John