I would walk her up to it and every time you feel her bunch up ready to jump back her up several steps then re approach. I would ask her to cross it as many times at it takes in a single day till she tires of jumping and decides it might be okay to stick one foot in the water. At that point praise her.

Just my two cents.

If you need something extra to hold on to over the jump you can buy a dog collar to snap around the gullet. I've always been told Cowboys used to have these as a bucking strap when they broke colts.

I would try starting with puddles, getting her to walk through a mud puddle, and then move onto the creek, walk her up to the creek, stop at her comfort zone and let her just stand there and calm down. Then ask her to take one step forward, stop her and again let her calm down. If she starts to jump go back to the beginning at the creek in her comfort zone. You might also try being on the ground on a lunge line and keep working her up and down by the creek moving her feet. There are several things you can actually do to desensitize her to the water. The main thing is to be patient with her, if you can get her close enough to the water to sniff it, her feet might follow!! Just take baby steps to getting her into the creek, and don't force her.
Running Frees suggestion is good too!!