I would treat this really differently depending on if it's anxiety based fear vs attention seeking. I guess that's where I would start.
If it's attention seeking - I would not reward her behavior - I'd reward it when she didn't act up.
On the flip side, I have a little one who had anxiety. Not major, but it would flare up at times. She became fixated on one concern. And would become very distraught. We've since had her in a program and it's really helped.
Originally I thought the thing she fixated on was the problem (bus) but it wasn't. She had underlying anxiety. I don't know how long I thought of ways to fix the bus problem, but it wasn't helping. That's when her teacher suggested she might benefit from our anxiety program.
What we do - with the anxiety program - is listen and validate their worries.
Then you go through their concern and the worst possible scenarios. They tell you. So if your daughter said "My worst fear is that the little girl would not get help and would die" then you say "Do you think her mom would be there, or someone watching her?" And they say "Yes, I think so". So then you say "Do you think the mom would do something?" and they say "Yes, they would take them to see a doctor.." and so on ... Once you do that a few times, the kids can do it themselves. See that their fears can be handled. It's not about getting rid of the fear so much as teaching them coping techniques to handle them.
It's a simple technique but has been highly effective for our little girl.
If she gets hysterical, you do deep belly breaths. You can google this. Milkshake breathing.
But I'd try to figure out if it's just a habit that has formed vs an underlying problem. How's her eating? Any other outward signs of upset? Good luck :)