Ok, please forgive this if it's a bit basic for you,but in these situations i'd check
1.) The intonation- see here for how to do it
http://www.o-ma.com/hog/techtips.html#1
2.) That the string isn't wrapping back around itself and slipping.
If these are ok and she still does it, come on back..
cheers.
Accuracy,you say? hmm interesting concept..
