I am sorry to hear that your girl didn't make it. Bless your heart and your chickens.
2 weeks ago I had a RSL suddenly die. There had been no apparent sickness, cuts, or anything that I could see. I just went out to the coop like I do each morning. After I open their hatch for them to go into their runs I always go inside each coop and chat with them and look at everybody to make sure there isn't any visible signs of fighting or pecking. Nothing seemed out of place except one of my RSL was kinda huddled in the corner with each of her wings keeping her upright. I immediately picked her up, looker her over and brought her into the garage, made her a nice comfy bed, with vitamin water, food, yogurt, but she passed right away, and I have no clue of what. We got her from someone in 2008 so he only said she was like 1 1/2 years old. I think that was older because the other 6 haven't been laying as well since before summer. (which is fine with me, I plan to let them retire and have a happy wonderful life as long as they live)
My husband dug me a hole the next morning and by the time I came back from takin the kids to school the hole had filled with water. We have only had a round a million to many inches of rain not to mention the snow... so I had to dry out the hole and I lined it with slate rock, wrapped her in a big comfy blanket and wrapped her in a large plastic bag. It is so not the normal 'burial' my other ones have had but it was the best I could do and didn't want to freeze her and wait til the ground dried out. She is at peace and not suffering.
xoxoxoxoxoxoxo