Walk away Alex. You don't want to inherit someone elses problem. She should take it up with the other cleaner and/or seek legal advice. If you had a problem yourself with, say, British Gas, would you ask your local plumber/gas fitter to sort it out? No, you'd go back to British Gas.
I'll give you one of many examples why you should walk. You go in and clean. You may produce a great result. But, as A.N. Other has used steam, he may have damaged the heat set to the yarn. Next week/month/summer Madam notices that the pile is "bursting". It was alright after A.N. Other cleaned it, so it must be you who caused the damage.
Safe and happy cleaning:)
Ken