Oh Shauna I'm so sorry, I know how sad you must be feeling. I am sorry I hadn't responded sooner, we were doing the whole SuperBowl thing and I just got home and saw this .. I had to look twice at the title and name that posted it, since I know how careful you are with Missy.
It will be okay, she probably tore a ligament or sprained it a bit ... I remember when Gucci hurt his leg and how scared I was he was yelping and crying like NO TOMORROW and when I put him down it would fold under and he would immediately fall over and cry
. The vet did the same for us and said it was likely just a soft tissue injury and it would heal on it's own. He was on bed rest for a full week and he was so sad that he couldn't come out and play.. even though he was using it mid-week he wasn't allowed to, otherwise the vet said he could make it worse and end up having to get surgery etc. It was a tough week but I was so happy when he was finally better and able to use it.
You will see, Missy will be Ok she will bounce back and by tomorrow will be so much better. Please send her get well wishes and hugs and loves from Gucci and I!! You are such a good mommy, she is lucky to have you.