If you use Calibre to upload books to your Nook, you can download the Nook for PC application which will download all your books to your computer. Then, you can email the book file to your friend and she can use Calibre to upload it to her Nook. It is VERY simple to work around the lend feature. The way I see it, if I bought the physical book, I could lend it to anyone I wanted. I shouldn't be limited because I bought it electronically, especially when their profit margin is higher for e-books.
Have you actually done this?
Because having had trouble opening books on my DS' Nook that we bought because the email they were purchased under didn't match the e-mail that the Nook was registered to, I don't see how this will work, unless you are stripping the DRM from your e-books by using Calibre.