I personally wouldn't wait around for who knows how long for another appointment. She's demonstrated that she's 1) got too many clients on her caseload and 2) that she won't think twice about cancelling you two times in a row when she isn't even sick. Having too many clients on her caseload doesn't mean she's good, it just means she's irresponsible and client wellbeing is not her primary concern. See if you can find a different therapist who will show you more respect as a client seeking services.