If the pizza place is next door maybe she can make a deal with them to temporarily use their handicap restroom until she can put one in and find out if the inspector will let her do this until she can put one in.
Also, she really needs a 36 inch or 42 inch wide door to the bathroom and a railing on the wall next to the toilet
There has to be room to turn a wheelchair in a circle, typically 48-inches. Then there’s the size, shape, and height of the toilet and the sink. If the plumbing is exposed under the sink, then you need to insulate the pipes so folks can’t burn themselves when they roll up to it. But still $10,000 is a lot to bring it up to code, unless it’s a really old bathroom.
That solution is not very likely and is not an option unless the bathroom is designed to be a shared facility. As in a multi tenant building where a restroom is accessible from the interior of the various tenants.
ADA says you need a 5’ diameter turning radius...
impossible in many old bathrooms.