File and Folder permissions..

I have a 10.1 system at home that my wife and I share. I set up a
directory /home/shared where we can put shared stuff like mp3s or
pictures. I changed the group on the directory to users and set the gid
bit so that all files created in that directory will be with the group
users.
Here is my problem. When I put a file in there the user is me the
group is users but the permissions are 644 so she can't delete it or edit
it. I have two solutions neither of which are what I want.
1. i can change the umask for users to 002 in /etc/profile so all files
are created 664. (but then she can see all my pr0n in /home/whitey)
2. I can cron a shell script to "chmod -R 775 /home/shared" every hour.(as
the directory grows this might get to be time and resource consuming and
it sets everything to executable)

Does anyone know how to set a umask for just one directory? I googled, but
found nothing.

Thanks.
.