The nickname is the issue, really.
Anything but
Sandra. I'm bored to tears by all the
Alex and
Lexie girls, but I don't mind the look or the sound. With
Sandra, I can't find anything to like.
A friend of mine is
Alexa; not short for anything.
Alexa Kirsten LN. I think that's probably the best alternative: ditch the full form and use the nick. Not something I often recommend, but this is a special case.