Ar you sure? that’s an 8 hour day for 12.5 weeks.
Most houses go up sooner than that, except for the parts she could not help with anyway (laying a concrete foundation, roofing, plumbing, electrical)
From what I have read about Habitat for Humanity, most of the “sweat equity” hours are performed on other people’s houses before yours is built. At least that is the way it was done in the early years of the program.