I'm so sorry, I was really hoping I would not see a post saying this.
It's very clear how special Wiggles was to you, and losing someone so special and important is really hard to cope with.
I know that 'what ifs' and guilt is all part of grief, but I also know that telling you that won't change how you feel, or make it any easier. Try to keep in mind what the vet said, and try to rationalise your thoughts with the fact that she has been ill for a long time.
You gave her a terrific life, she will have loved it so much,you gave her a dignifed and loving ending, and anyone would appreciate that.
I truly wish I could take away your pain, I know I can't, and I also know how insurmountable it feels right now. Please try to remember you have lots of friends and people who care for you and want to help if you will let them.
If you ever want a chat, my PM is always open. I don't know if you have read my Flash post, probably not, but my loss of him was probably similar to your loss of Wiggles.
Hang in there *hugs*