I spent most of my career in construction and most of the other time, in trying to encourage women into construction/running programmes to facilitate this.
From my experience, women are still seen as being there with the 'permission' of men, and have to work twice as hard to 'prove' themselves, have to work alongside the continual sexist and often disturbing attitudes of people who should have your back, and in the end, often just give up and go work in offices.
And that's before the long hours to get jobs done especially in the summer, and the potential to have to move around or work away for long periods on jobs around the country.
However it can be exceptionally rewarding, particularly seeing projects that you worked being used by hundreds of thousands of people every day.
I'd recommend that she take advantage of an apprenticeship in a medium to large company, learn as many aspects of a trade that she enjoys, and then aim to set up on her own or with a partner, mainly for safety reasons, and then work for herself. Plumbing and P&D are often good trades to go into as the materials are not quite as heavy as other trades.