I'm assuming she's a True Blood/Sookie Stackhouse fan, no? I have only heard this name once--on the main character in the Charlaine
Harris books which is now a tv series on HBO. At first glance, it looks like
Sue + Key, but it actually rhymes with "cookie" and "rookie". On the tv show, when some of the characters say the name (esp. with thick Louisiana accents), it sounds more like "Suckie", which is interesting, seeing as it's a show about vampires. :b I think it makes an ok nickname, preferably for a pet, though, and not a person. I think it makes a horrible given name for a person, just to go on the record. I will second (or third?)
Susannah, as that's the only thing I can think of it could slightly be short for. And
Sukie is a nn for it, I believe, so that's really not a big stretch after all.