Addressing a widow who lives in Poland

I am writing to a recently widowed cousin in Poland. How do I addres the envelope? Do I use her given name or continue to use her husband's as we do here in the US?

you seriously in the US use the husbands name to address the wife? like Mrs. John Smith? even when she is widowed?
good grief it is 2012 you know.

Yes, We still do. Good manners are still important.

It has nothing to do with good manners as such, it's just a convention. I'm surprised American women haven't gotten rid of that one yet! Anyways, in Poland you never ever address the wife using the husband's given name.

E.g., if Alina and Jakub marry, and their surname is Nowak, then:

It is pani Alina Nowak and pan Jakub Nowak or, if addressed as a couple, państwo Alina i Jakub Nowak or Nowakowie / państwo Nowak / państwo Nowakowie.

Good manners?!?
Even if the husband was alive, you should not use her husband's first name when addressing her. She has her own first name, for Christsakes!

When addressing both, use, for example "Mr and Mrs Joseph and Cheryl Novak"

it is not good manners to behave as though a woman does not have her own name. sorry.

Just to remind our British members of Princess Michael of Kent, the couple being Prince and Princess Michael.

My granny hated it when people stopped calling her Mrs John Elliott. She felt people were forgetting her late husband and she wanted him, and their relationship, to be remembered.

Maybe, then, and older generation thing. Or just an older people thing?

My ex-wife was/is Mexican, where the tradition is that she has a long name containing both her father and mother's surname. When we married, she added mine, prefixed by a "de". Her mother, a widow, was Paulina (maiden name) widow of (husband's surname) So on, letters she was Paulina X Vd de Y

definitely an older person thing and perhaps a royal thing, who knows, they are not really human anyway..;0)

We have a little bit different system(or had)
Jan Nowak
Alina Nowakowa-Alina that is married to Mr Nowak
Helena Nowakówna-Daughter of Mr and Mrs Nowak-unmerried
But from what I know it was rather used in speaking than writting.The first name was always the same only the last name changed.

Whew! At least she gets to keep her first name! ;)

It also worked in different situations:
Doktorowa/doktorówna-wife/daughter of the doctor
Dyrektorowa/dyrektorówna-wife/daughter of the direktor
and so on.

Actually the doktorowa , prezesowa, profesorowa (or inżynierowa - drives my mum crazy) are still sometimes used. We have prezydentowa - wife of president.

And there used to be that Tomaszowa, Józefowa, Karolowa thing, but it went out of use even before surnames with -owa and -ówna