I miss some information for a better guess...

Is this shared hosting? I guess so, because usually one would not configure Apache to run scripts under a login user.

Do you have admin rights? This is uncommon with shared hosting. If no, then it is no surprise that you can't run chmod. You also need admin rights to create a new user. This may be trivial, but changing the name in /etc/apache2/envvars does not create that user. If you do have admin rights, try hippo's suggestion to give Sally1 the same numerical user id as you have. Check out the command usermod, giving your numerical user id as --uid and don't forget to specify --non-unique.