You said your NPC name is "Sabrina nightingale", but I assume you mean "Sabrina Nightingale" If the last name isn't capital on the NPC, but it is on the script, that will probably cause it to fail.
Also, scribespells() requires a level argument, and you have a colon there as well, so change that to this:
Code:
plugin::scribespells($ulevel);