My thought is that, since this is a pattern of absent behavior on her part, perhaps rather than email her, it is time to speak to whomever it is that is her supervisor.

It doesn't sound like it is about you coming last so much as it is about whatever her issues are coming first. Even if those issues are legitimate, they are still affecting her ability to provide consistency in her therapy practice, and ultimately, in their clinic.

Put it on record with her supervisors. I'd save talking to her about it until you get a response from them at least.