Does anyone know how we get a reply to this? Reactivating a fairly old thread. Just checking that you mean the original post (problem using different Adobe IDs) rather then the second post (problem using the same Adobe ID).
As long as you can monitor the copying of the books from the computer, your best bet is just to use a single AdobeID for both Nooks and the computer.
Make sure your more adult books don't get copied to her Nook.
If that isn't practicable I'm not sure what to suggest.
Unfortunately the Adobe DRM infrastructure is very inflexible (and its implementation is very flakey, especially in ADE2.0).