I would have just placed an incident light meter in front of the model, pointed toward the camera, using a reflector to bounce sun light on her. The incident metering will place the skin tone just right and make the backlit hair "shine" which I suppose is the intended effect (not entirely reached, which makes me think the exposure is actually a bit too scarce for the shot). The dynamic range of the negative colour film would hopefully retain the detail on the vegetation behind, which should be around 2.5 EV above the shade and well inside the negative film comfort zone.
Personally I would place the model hands differently so as to avoid the risk of blowing the highlights on the hands. If the hair have to "shine" in contre-jour, they should be the only part directly hit by sunlight.