While you could list it on bizbuysell.com or similar listing services, I think a well-placed ad in the various physical therapy publications and associations would do much better. For grins, here's a list from
MergerNetwork
She is selling her customer list (goodwill). I've seen quick ratios on revenues from 40% to 60%. But the depressed revenue of the last 12 months, no matter what the reason, is not going to help.
Given the personal liability of the business, I don't think I'd do a partnership as stomachmonkey suggests unless she knows the PT very well. But she could structure a deal where she takes control of the business unless payments at a certain level will be met. And her landlord will need to be willing to assign the lease to the new PT - that might not be trivial either.
In the best case scenario, she'll need 2 to 3 months to find a buyer, reach a deal and have the buyer secure some amount of financing for the down payment.
With just 30 active clients, frankly I think she'd be better off finding a local PT she likes and introducing her patients and ask for a declining revenue share for one year. And sell the equipment to other PTs.
Just my $.02