we got a small one like that and no yolk, i cooked it and mixed with the scarch, we have a dog that goes in yard at night and gets chickens out from under coop, it is to cold for them to sleep there this time of year, our dog has been good with them helps us round them up if any get out, but on the other hand i would never leave him out with them, i do think he would try to play with them and hurt them. we never even leave him out of the house with out us, and i have great grand babies that come over just to get eggs out of coop, never slowed down the laying.Is her leg injury permanent or broken? Or do you think it's a bad internal bruise? Poor sweetie! If she is permanently disabled she will need a gradual ramp to climb to the new coop's nestboxes. To not get picked on an injured bird will endure a lot of pain to keep from looking ill so they don't get pecked by other chickens. She should be isolated indoors and watched to keep her calm while recuperating so her injury can heal and not cause her so much discomfort outdoors trying to keep up her appearances in front of the flock. The roo could hurt her more during mating too. It wouldn't hurt to separate her from the others for a few days since the roos have no sense to leave an injured hen alone. This is one reason I like Ameraucanas and EEs in my yard -- they accept orphaned chicks or injured birds into the flock without incident where other breeds are not nice about it.
There's nothing wrong with the egg except maybe some extra stress hormones in it -- just guessing here. Notice how much darker the mini-egg is because there was less egg surface for the pigment to cover so it came out darker. The egg is fine to eat or if you feel better not to eat it just hardboil it and feed it back to the chickens in their treat bowl. It looks like the size of one of our Silkie eggs!