I don't think it's worms. If she was infested with worms, you would likely see weight loss and worms in poop. Most birds carry worms anyway, it just isn't a problem unless they get overloaded. She isn't showing any respiratory problems other than the panting? That's normal in heat. It very well could be heat stress and her consuming extra water. You could just wait and see. My next guess would be an e-coli infection. There are medicines out there that treat for that. May have to look online. It's best to have a few different meds on hand when raising chickens so they are there when you need them. Usually, there are waiting times when getting meds for chickens so I always have something on hand. The biggest selection is found online.
Let me clarify what I said. By waiting times I meant shipping and such. When you need a medicine for a chicken, time is not on your side. The hide their symptoms and it is usually too late by the time you notice anything. Unless you are very observant of eating habits, stools, appearance and behavior.
The reason I think e-coli is I had a rooster alone in his pen that had messy droppings. Dry enviroment, just him, his water and feed. Yet his droppings were runny, not firm.
I put him on a medicine that treated, cocci, crop canker, e-coli and one other thing(can't remember) for the five days stated. It cleared him right up. Droppings returned to normal. Now, it wasn't a medicine specific for chickens, but it was for birds.