I encourage her to consider civil engineering with environment focus, but one post indicates that there might be saturation in this area.
A lot of places have spun off Environmental Engineering so it is now it's own discipline, and no longer under Civil. it has it's place, but what I see in everyday practice now is that many subdisciplines of Civil incorporate environmental into their work. You have to here in the US, as the building codes have a lot of requirements.
If you get into site development, a typical building site plan for DC now has many drawing sheets related to runoff, retention, etc. Pages and pages of calcs that used to be covered with a single sheet a few decades ago. It is much more technical than it used to be.
Just about anything you design has to earn LEED points, comply with energy and environmental codes, Energy-star, etc. In fact if you want to be a Civil and not need any environmental you are probably SOL. I think the 'real' Environmental Engineers are doing the big impact statements for heavy construction, new roads/ bridges, etc.
Construction is booming in the mid-Atlantic area. Hard to say when it will eventually correct. But when I go into construction trailer complexes on large jobs half of the construction engineers are women. It is no longer the realm of 6'-3" 285 lb men who direct the subcontractors mainly by physical intimidation. No more fist fights, throwing subs out the door, shouting matches, etc. And the construction engineering jobs are great for people who want office + outside time, and they pay very, very well in times when construction is really rolling. Construction Engineering, like Environmental, used to be a sub-discipline of Civil at many universities but has largely moved under the umbrella of the construction major. I have seen some places that provide dual majors so you get Civil - Construction Engineering degrees.