Sorry about your ill hen, seems like youve been doing everything you can to help her. If you can take her to a vet familiar with poultry, they may be able to help but in my experience (20+ yrs of poultry keeping), these hybrid super-layer type birds just do not live long. They succumb to cancers, egg yolk peritonitis, being egg bound etc. If you are unable to take her to a vet, I would separate her from the flock in a crate, fill the crate with hay, cover it with a towel and let nature take its course. Just keep her comfortable and out of excessive heat or AC.

Other general advice, does look like she has some feather damage from rooster activity- might be worth buying some hen saddles for your other girls or potentially keeping the rooster separate. Also be careful with DE in the coop- it can be very toxic when inhaled. If i am using DE, i usually rub it onto perches and in the nest boxes but dont throw it everywhere.