I'm so sorry you had to let your little girl go. It's so painful and lonely without them.

But take comfort in knowing you did the best you could for her and you helped her at the end when she needed you.
I had to let my poodle of 17 yrs go last winter and it still hurts and I still look for him some days. But it's not so painful now and the memories are good.
It's nice that your husband loved her too. You will be able to remember her together.