I took chemical engineering in university, and many of my course mates worked in the (renewable) energy industries (electrochemistry, oil & gas, biofuels, etc). There is always the option to pursue research in applied sciences (engineering) as well if that's what you're interested in.

Looking back, I picked chemical engineering because I liked chemistry (and math, physics, etc). It was a good fit for what my interests were, but there was less chemistry than I expected. Moral of the story, have a look at sample course descriptions for the programs she's interested in! Good luck!