1. Let her sing without you playing, the tune she is having trouble with.
2. Find out what key she is singing in.
3. play an intro in that key let her sing and see what happens.

Give her a few shots. If, after playing the intro like I said and she sings in a different key after several tries, like Gary said, she's helpless.

Some people can listen to a note 50 times with 50 tries and can never hit the note on pitch.

I hear people talk about so and so has perfect pitch because he can sing any note you name. I can do this and I'm sure others here can do it also.

HOwever for me to do it you have to hit me a C note to get in my head and then I can sing the dom 7th, MAJ 7th so on and so forth. Those of you who think you can't, practice it. You'll be surprised.