OK - start with it wet, and clip back the hair on either side of her fringe that you don't want to cut. Comb her fringe down, and with very sharp scissors, and without taking too much off, start from the MIDDLE and go out the way to one side. Repeat on to the other side.
I am the fringe meister - never had a disaster using this method (although the hairdressers out there will probably be horrified!)
do you have a steady hand and a sharp pair of scissors and will she sit still?
I've cut dd's fringe loads of times. You just cut it straight just at the eyebrows (leaving room to make it shorter if you cock it up) and then take little chunks out to soften it. I do have a pair of hairdressing scissors though.
O o o o h... this I do know! My mum use to cut our fringes throughout our childhoods with the tried and tested SELLOTAPE method. Wet hair, comb fringe section neatly forwards, apply long single strip of Sellotape across it at the level you want t ocut and use lower edge of tape as a guide. It holds the hair in place so that you can see any straggly bits and nip 'em.
DD will enjoy this herself when she has enough hair to warrant it; it's a winner!