Time with clients--thoughts?

I left a position in which i was doing CEO work for teacher money after 5 years with a very small business when my boss refused to let me work ONLY 40 hours for a while because i was burned out and he was acting like a child & taking advantage of me among a bunch of other stuff that had escalated over 2 years. This happened about 3 months ago and i am kind of still recovering emotionally. I have landed in a space where i am a small business consultant (a lot odfpeople could see the work i was doing in my previous role and how beneficial it was to that org, and have reached out for advice or to hire me, wild!), and i LOVE it. One of my clients was no call no show for a meeting yesterday a.m., so i waited 15 minutes, then left. She texted me 20 mins after our meeting was supposed to start and said, "hey i am on my way!" I said, "oh, i waited 15 then left!" She said, "well can you come back?" And I said, "i'd prefer to reschedule, here are some times i am free this week." I thanked her for her flexibility and for being the kind of person i can have boundaries with, and explained that my former boss used to make me wait without letting me know all the time, and that i learned that i have to respect my time or i can't expect others to. I was not trying to compare them, just trying to explain why i was holding the boundary about my time, which i also realize was not necessary, and it is my people pleaser habit coming out in the middle of my attempt to hold boundaries. Anyhoo, then she got defensive and was like, "well i'm not him." And i was like, "you are not, thank god!" And changed the subject. She is kinda difficult in other ways, too, like she isn't great at communicating and then seems frustrated that i am not a mind reader. So i don't know how sustainable this particular relationship is for me, to be real. But i think i need to put something in my contracts moving forward about time and under what circumstances i am willing to wait and for how long. Same as like doctors and therapists and lawyers. Because i absolutely understand how difficult it is to juggle all the things as a small business owner, but this has to be a mutually respectful relationship. And time is seriously small business people's most valuable asset. How do you all handle this when you are consulting?