Go to XXX and tell them that you were informed by your supervisor that there were some mistakes found in some of the recent documentation that you had edited. She was unable to provide you with specific details, but you prefer to do a thorough job, and wanted to make sure that the errors were corrected. Also make sure that XXX knows that you are very willing to fix any errors that are found, but that when you don't know that there is an error, you can't fix it.
Basically go over her head, but do so in a way that makes it clear that going through her was just not effective. Make sure she is the weakest link in the chain. Either you'll be directly contacted in the future, or your supervisor will become the little messenger girl between XXX and you. (who's working for whom then ? LOL)