ADA says you need a 5’ diameter turning radius...
impossible in many old bathrooms.
And if she had just moved into and existing occupancy and not made any changes she would have been o.k. Even then alterations don’t trigger every requirement of the ADA. An alteration to the primary function area triggers a priority of ADA requirements, those include providing handicap bathroom(s). Even then changes that are disproportionate to the overall alteration are not required. Changes that exceed 20% are considered disproportionate. So she would be required to make as many changes as possible without going over the 20%. Those changes in order of priority are entrance, path of travel to the primary function area, restroom/bathroom, ...
So if there is an existing bathroom and it would cost her more than 20% of the overall alteration to expand it that would not be required. Instead if the entrance is o.k. and the route to the dining area are ok. she might install grab bars. Provide a handicap accessible sink and water closet. Install an accessible door and if necessary widen the entrance to the bathroom. Now here is the rub.
It could be that a local ordinance has stricter requirements and makes it so changes to the primary function area triggers stricter compliance with ADA. For instance altering the entire bathroom space not just fixtures.
The good news is that if the requirement is that she provide a fully accessible bathroom (as in new construction) there should be a means to request a variance or exception. Again this is for local ordinances.