Unfortunately at this point, you are just one more empathetic victim to someone elses pure stupidity. Regardless of how thin the animals may seem, unless they're being visibly starved or abused, animal control doesn't have the right to do diddly squat.
I would do my best to talk to her, and if that doesn't work, distance yourself from the situation.
And for the record, Haflingers, like almost EVERY breed, contains a hearty portion of Arabian blood from centuries ago when they began developing the breed. If she's trying to show off how smart she is, she's failing miserably as it's a pretty lame argument as to why to breed your mare to one - they obviously look nothing like Arabs at this point for a reason.