Metering for the ice. Spot meter on the subject. Since the lighting looks pretty even, you could have her stand still where she's going to do the trick so that you can get a spot meter on her face. Then make the manual settings to get the proper exposure. Then let her do the fancy stuff and you should be exposing correctly.
Canon 6D, Canon 5Dc, Rebel T2i, Canon EF-S 10-22, Sigma 35/1.4, Olympus OM Zuiko 21/3.5, 24/2.8, 28/2, 40/2, 50/1.4, 50/3.5 macro, 100/2.8, Canon EF 20/2.8, 35/2 IS, 40/2.8, 50/1.4, 85/1.8, 200/2.8L, Contax/Zeiss 28/2.8, 50/1.7, 85/1.4, 135/2.8, Soligor 135/2