Question about addressing outer and inner envelopes...

If someone is a widow, what do I put on both the inner and outter envelopes of the wedding invitation?

Outter Envelope:
FIRST NAME LAST NAME
or
Mrs. FIRST NAME LAST NAME

Inner Envelope:
Mrs. LAST NAME
or
FIRST NAME LAST NAME

i dont know 100% but my mom is a widow and she would get things that said Mrs. Susan Doe

A close family friend also lost her husband last year. We chose to address her as
Mrs. (last name)
both on the outer and inner envelopes...

Now that I got this book, Crane's Wedding Blue Book - The Styles and Etiquette of Announcements, Invitations, and other Correspondences, I read it all the time to see what the 'right' thing is to do for addressing as I edit our guest list.

According to this book, the outer envelope addressed to a widow should read as:

Mrs. John Smith

and the INNER envelope should read as:

Mrs. Smith

I would imagine that as long as she keeps the last name of her husband, that that is why HIS first name goes on the outer envelope. Having just lost my Dad last month, we had discussed how our wedding invitations would read. We agreed, and the book confirmed, that 'Mrs. John Smith' would be listed at the person who is inviting/making the wedding.