I wish Daisy the best in her healing and thoughts are with you.
I understand how hard it is not to blame yourself, us as humans tend to do that for those we love as it is in our nature. Just know, Daisy does not hold you in blame I am sure and as you can see by her "protection" she adore's you.
Bless your friend for all she is doing by sending flowers, covering vet costs, etc. She cares so much doesn't she?
Best of all I compliment your vet for going the extra effort and finding differant advise from other's educated in the best care for Daisy, he sure needs to be commended!!
I will be thinking about Daisy and from what I've learned from my vet as Schatzie had leg problems, even with a bum leg a Yorkie can live a very healthy, active life with much happiness!
Rest your heart and know we all here are thinking of you.