Both of my boys are much like your daughter. They are extremely imaginative and compassionate, although they are older than your daughter (9 and 15).
I was also much like your daughter. I had a stuffed mouse that I was extremely attached to, and I kept it well into adulthood which is quite unusual for M.. I'm the opposite of a pack-rat, and seldom keep anything. When I was almost 30 years old, we were getting ready to move into a new home, and I found this mouse in my closet. I decided it was time to get rid of her, and I threw her in the trash. I was in cleaning mode.
My husband found M. in our room hours later, sobbing. I couldn't believe I had thrown out my beloved mouse. I knew she was J. a stuffed animal (for goodness sake, I was almost 30 years old!), but I felt so bad about it. He suggested I get her out of the trash, but I had tried that, and she was too dirty. I had thrown her on top of a bunch of food. I left her in the trash, and felt awful for days.
On my 30th birthday, I opened a gift from my husband, and it was the mouse. He had gotten her out of the trash and had her professionally cleaned. I felt such a sense of relief! It was one of the best gifts I have ever received; I really married an amazing man! Now, almost 13 years later, she sits proudly on a shelf in my closet, and I feel so much better knowing she is there.
Your daughter will likely feel that same relief knowing that the other stuffed animal is in good hands. Some of us do have very active imaginations and such strong compassion that it reaches to inanimate objects. We do know the difference between reality and fantasy, but still . . . :)
Your daughter sounds lovely.