John wrote:

I've used rules to require Me@ emails to go to my Inbox and Wife@
emails to go to Wife Inbox. That seems to have worked but I get 2
copies, i.e. Me@ and Wife@ appearing in each Inbox.

Make sure you include the "stop procesing more rules" action on each rule.

In Tools/e-mail
accounts, 'view or change existing e-mail accounts', hitting 'Next' I
can see both Me and Wife, with Me as default, AND, 'Deliver new
e-mail to the following location' shows Me-Inbox, but although there
is also Wife-Inbox, it seems that both Me and Wife have to be linked
to either Me-Inbox or Wife-Inbox, there seems no way to link Me to
Me-Inbox only, and Wife to Wife-Inbox only. Maybe thats why I'm
getting 2 copies.
I fear I have done something idiotic when first setting up Me and
Wife.

I don't think you stated whether or not you use the same username/password
to access the two mailboxes, so we don't know whether or not the two
addresses are aliases of each other, but I suspect so. Also, you don't say
whether or not you've tried separate mail profiles.
--
Brian Tillman