...wondering how she can send me a file I can work on - we have fonts taken care of with OTF... thanks!
cross-version collaboration is noty a great workflow, but if your coworker exports to .idml and sends that you'll be able to open it. There will be some text reflow most likley, and if they used any new features in CS5 that will be lost entirely.
Before your coworker does this have him/her package the ID CS5 file.
Then open the packaged file and export that to IDML into the same folder.
Then zip up the whole thing and send that to you. This will assure you
have the links as well as the ID file.
Other caveats have been covered by Peter.