You said she was straining in the nest? And her vent is beginning to protrude? That would be a sign of an oviduct obstruction.
When I have a hen with these symptoms, aside from the possible ascites, I give a calcium supplement immediately, then a 30 minute soak in a tub of warm Epsom salt water, then dry off and place the hen on a heating pad (moist heat if possible) in a crate in a quiet place. Lubricate you gloved fingers with a water based lube and feel just inside her vent for the egg, noting where it is if possible.
Then leave her to rest, but check on her frequently. If the egg gets stuck in the vent, you may need to intervene, but hopefully she'll pass it.
We'll stand by for further developments.
When I have a hen with these symptoms, aside from the possible ascites, I give a calcium supplement immediately, then a 30 minute soak in a tub of warm Epsom salt water, then dry off and place the hen on a heating pad (moist heat if possible) in a crate in a quiet place. Lubricate you gloved fingers with a water based lube and feel just inside her vent for the egg, noting where it is if possible.
Then leave her to rest, but check on her frequently. If the egg gets stuck in the vent, you may need to intervene, but hopefully she'll pass it.
We'll stand by for further developments.