sad and a little confused

Hi byc friends
I just had a very sad experience, my baby girl Olivia, my lavender archana,(not sure if I spell it that way) had to be put to sleep. I noticed she was sitting down way too much so i kept an eye for a few days then today when I went to open the coop door I noticed she hadn't moved all night and she usually sits up and roosts but she wasn't. I felt under her tummy and she had a full sack down near where I imagine her eggs start being made. She had no interest in walking, I put her on the grass to follow her partner in crime but she just sat down again. The Bird Dr checked her over & said it's a disease in the yolk making section of her reproductive area. It was going to be more than $500 to see her well, including surgery then an implant to stop her eggs plus anti biotics all with no guarantee she will make it. I won't put a small bird through that so she's now asleep
Can anyone advise how I integrate a new friend in for my chook Daisy? The lavender bird has now gone to sleep, Daisy is the one alone but I'm not sure what breed she is. Any advise appreciated

 

Thankyou so much, I'm still in tears, but my hubby buried her a moment ago for me. She's under her favourite tree near her chook house. She was such a placid little darling, and loved being held so we will miss her dearly and I feel dreadfully guilty knowing if I had just made sure she had enough calcium it could have been avoided. A Cochin? Yes that rings a bell Thankyou so much I will take your advice... xx