Gwen-death of my beautiful girl

Gwen is a chicken or hen. Gwen died today. She had freedom less than one year. She came from a battery farm via the Little hen rescue. I had her in June last year with 2 other girls and then 3 more a week or so later. Three weeks ago I took her to the vets convinced she had gapeworm. She kept opening her mouth. The vet said the wormer I had been giving her was fine - she had it once a month as directled on the bottle and the vet looked down her throat and saw nothing so said I was wrong and she had a mild infection. She gave gwen antibiotics. Gwen got better. She wen back in with her friends having spenst a few daysin my kitchen. Then she was suddenly ill looking so I tok her out this morning. By lunchtime I was very concerned and phoned the vets. Instead of going to the local office who I was sure had got it wrong and I was still convinced gwen had gape worm so we took her 40 miles to warwick which is teh head office of our vets. We saw a vet who knopws about chickens. She confirmed I was right - me who knows nothing about chickens!! Obviously previous vet must have been incompetant- and gwen has a chest infection. Gave er antibiotics and this time a new wormer since the one I was using DID NOT kill gape!!!!! I was using vermX. The new one is flubenvet and states on it it kills gape amongst other types of worms. Its a white powder you mix into their food. Gwen had an injection - all in all these 2 visits cost over £70. We get home and are there about 2 minutes wne gwen has a sort of fit and just dies......................
I am so upset..............