Christine,
There seems to be two things at play here: The first that someone is "taking credit for your work;" the second "ethics."
From the "taking credit for your work" perspective - that happens all the time if you work for a larger organization. Sure, you may get a kudo or two for a well-run project, but your intellectual property generally belongs to the company; so they are in fact taking credit for your work, every day. That happens all the time in every profession. Having experienced over 60 revolutions around the sun, been through graduate school and other experiences, I've learned to not worry so much about that. I am also lucky enough to have a great group of colleagues (who are all independent contractors) and we use each other's work constantly because we recognize that our jobs are, in the end, about other people's health and environmental well-being.
With respect to ethics - PMI Is the final arbiter of that (both before the test and after), and better them than me, I say.
Finally, keep in mind that there will be unintended consequences of unnecessarily raising a red flag ("Unnecessary" here is my opinion). Up to, and including, losing a friend/colleague.
Ultimately, the choice is yours. I've told you where I'd go with it, but it's really up to you.
Harry
+++++
Harry J. Elston, Ph.D., CIH, PMP