Theres no way to help really, no matter what I say it won't magically make it better. Only time can heal this kind of pain. My Golden Retriver was put down a year ago, it was horrible. I had her from like 4 er 5 to 16. I loved her, she was very loyal, extremly protective of me, I remember I used to lay my head against her chest and use her as a pillow when I was watching T.V or a movie at night, I'd usually fall asleep and she.....would...not...move, wouldn't not an inch untill my mom would come and get me.
Now I just moved out so I can't see any of my dogs not Carlie (pure bred minature poodle), Keyna (pure bred black lab) or Missy (multiese, poodle mix).....I miss them allot.
I'm sorry that this is happening but if shes older then you and your 13 then she is really really old for a dog and I understand putting her down, it comes to a point where your keeping them alive for your sake not theirs. Brandy was really old and in allot of pain when we had her put down she had had 2 dislocated hips, a twisted gut, broken leg and somthing else when I was younger......So anyway it got to the point that she couldn't even get up I would literally have to pick her up onto her feet and then I'd have to stay close and watch her cause she wasn't very stable. It was my parents that made the decision to have her put down and at the time I HATED them for it but now that I look back I understand why.