I'm so sorry to see your news. She had a good life with you and you made the best decision for her when the vet could do no more. Try to concentrate on remembering the good times.
My heart really does go out to you - it is a dreadful situation to be in. I lost my old boy in an almost identical situation, so I do understand how you must be feeling.
Please be kind to yourself, and rest assured you made the best decision for your little mare. Sending you lots of virtual <<hugs>>