I'm going to guess that in a multi million dollar home, these aren't cheap mirrors. Well eating (or even close to eating) 4 nice mirrors probably wouldn't be fatal to my shop. I do think it could start a chain reaction that would be fatal to my shop.
Note to self: Don't let this happen to you. Put a disclaimer that clarifies that because the designer is familiar with the project, and I am not, they are responsible for any oop’s, afterthoughts, changes, mistakes, errors, mental lapses, bad ideas, bad choices, sizes, colors, shapes, types, textures, smells…….
Carry on.