Oh damnit. I’m so, so sorry to hear it. She was really a lucky dog to have had a mama like you and you were lucky to have had her. I hope she finds my Rottie Amos on the other side. He was a good boy and would watch out after her.
Awww, that’s heart-wrenching. 
I’m so sorry to hear of the outcome. I was watching this thread for updates and hoping for better news.
Apologies if this is inappropriate at the moment, but I just looked at the pictures and wow, you’re beautiful! And Princess was quite a cutie too.