Okay, the eye shadow colour which suits her depends on the tone of her complexion as well as the colour of her eyes.
If she has 'warm' tones her skin will have a peachy/creamy appearance, so warmer shades will suit; if her skin is more blue/pink she has a 'cool' complexion, so cooler shades are best.
I'm the latter, and the make up artist (ahem) I saw the other week recommended pale pink, lilac, purple, navy, silver, grey, burgundy (not all on the eyelid, obviously).
I've been wearing shades of peach, beige and brown for years, and now realize that they were flattening me.
Also, if she has deep-set eyes (like me), she has to have the palest shades possible on the eyelid to bring them forward.