That is a very ambitious goal and goes well beyond a small business. My first question is if this would be best run as a business or non-profit? Knowing only what you described a nonprofit might be the way to go, which would change your funding structure, how much personal seed money you would need, insurances, how you structure and report your business - everything.
Or maybe you are looking at it where you provide the business space and contract with professionals to provide the services, and you take a cut?
Or are you going to be hiring specialized therapists and having them on payroll?
All of these would look very different, while books are a great resource, I would encourage you to look for small business incubators/mentorships/development centers in your area. Most offer free basic business classes. At the very start, she should be looking at writing a business plan so she can answer some of these questions. It's the first step to everything :)
As far as specific books, it's not so much a business book, but as far as the medical/social work/art therapy field and different possibilities and opportunities for partnerships: Creative Healing : How to Heal Yourself by Tapping Your Hidden Creativity
by Michael Samuels was a pretty good read.