The "trades" covers a lot of ground. Some of it is going to be hard on your body. But electrical is probably less bad in general. I also have a friend who is (or at least was) in the steelworker's union; she got into HVAC after Ringling Brothers clown college didn't land a permanent gig. She mostly does design work. Not everything is roofing, which as a peer wrote is probably fairly tough in general.
Sounds like she's got an office job that is not much different from what programmers do. I once spent 3 minutes in the attic while HVAC guys were replacing my unit. They were hauling/removing through a tiny opening in the ceiling and installing heavy stuff for several hours. And July in the South is not a 'recreational' season.
My point was that the trades don't automatically mean "hauling/removing through a tiny opening in the ceiling and installing heavy stuff for several hours" although they can. She does have to spend a fair bit of time onsite.
