There are some generalised housing mods that are reasonably one-size-fits-all, such as ensuring hallways in new builds are sufficient width for a power chair, ramps, etc. But certainly, for an individual, a needs assessment would be necessary and a house modified for their specific needs.That is absolutely not why she is doing it though.
A lift won’t be helpful unless the entire house is also being built for that. Handrails, ramps, a walk in shower, low benches, wide doorways etc. Isn’t it usually specific to the person’s needs? For example my house has features for an elderly person to get around easily and safely, but not a wheelchair user.
The lift they're putting in sounds like it's more about moving things between the levels than people, which can still have its uses in old age, as they can put shopping in the lift and have a stair-lift installed for themselves.