My sons have short three letter names on their birth certificates.
They're short versions of longer names (think Sam instead of Samuel for example, that kind of thing) but we didn't like the longer names so wouldn't have used them plus the short names go better with our long surname.
Remember it's her name, not your name. Trifles, After years and years of never using my full name, hating it etc, I actually find it quite useful now, it does sound more formal, makes me sound a bit more serious. I'm glad now I have that option.