Users Can't Exist in Multiple Client Companies?


I have a client, Jane Doe, that needs a personal website built for her,but also needs a website built for her band, AeroSmith.

In this case she is a user in the "AeroSmith band" client I have, but I'd like to make her a user in "Jane Doe ProSite" client as well. I'm not sure that I should be creating an entire separate client to take care of building her a personal website but that's a whole nother issue, because the bottom line is: she could want me to make a website for her band AeroSmith and a Website for the Local Chapter of her Organization.

In this case I have a user with the following credentials:
username: jdoe

I've tried, but failed:
-- find a way to make 'jdoe' exist in both client companies [this is the realistic approach]
-- find a way to _add_ a 'jdoe' to the second client company [obviously this won't work, because you'll get a, "error: email/username already exists"]