She seems to think there's room to maneuver. I'd make it unambiguous. Unblock her long enough to send an email detailing your displeasure at the attempted appointment payment bait and switch and annoyance at her passive aggressiveness and end the relationship.

Oh, and save the texts in question.

It doesn't sound like she will, but if she tries to escalate the situation and actually collect on her "gift" appointment, you have something to send to her bosses or even Medicare. (It is Medicare in Australia, yeah?)

Passive aggressiveness is one thing, but trying to worm your way out of an agreement you made just the week before is... just... wow. I'd say good riddance to her!