Help Sissy cross the rainbow bridge

Hi, this is Miss Dirty Face White Girl, aka, Sissy. She is my 12 year old boxer and she was born deaf. But she doesn't know that she can't hear and we can, as I've taught her sign language. Not real sign language, but stuff I made up to communicate with her. I saved her from a terrible back yard breeder situation and she was in terrible shape when I got her at just 4 months old. She had not been fed in who knows how long and you could see every bone in her little body. She had severe trust issues and would stand just out of my reach and bark at me when I tried to put a collar and leash on her. It took her a long time to bond with me. But once she did, she never wanted to leave my sight. I call her my velcro girl and I couldn't pay her to run away. She goes everywhere with me. But age has caught up to her and she can no longer control her back legs and cancer is setting in. These last few days have been rough as she coughs constantly. I have spent so much on her lately that my credit is maxed out and I am here asking for help to let her go with peace and dignity. Today is my birthday and all I want is for Sissy to have peace. Anything helps and we thank you from the bottom of our hearts.