You don't get over it. In time, the painful throb turns into a dull ache, but there will always be an empty hole. That is the piece of your heart Keena took with her when she crossed the Bridge. There will be a point where you are reunited. Until then, carry the love and share the love with others (as you are doing).
I lost my two Scotties in less than one year. It hurts. I still cry. I've said that when Tipper passed she took a piece of my heart; when Mac died, he took a piece of my soul. I guess in some ways I was lucky, my dogs were elderly, but really, be it 2, 12 or 20 are we ever ready to say goodbye to our best friend?
What I found that helped me was to write to them. I don't open my journal as often now, but I have a document on my computer that I just use to talk to them. Tell them the special things going on. My dogs were sick when they passed--we had to help them cross--so I wrote each of them a letter telling how special they were. They were buried with the letters. I know you didn't have that chance.
Don't feel bad that you haven't moved on in 8 months. Every person grieves in a different way--there is no time schedule. Give yourself the time you need. Many understand that you suffered a tragic loss of a family member. I'm sorry. Keena was a beautiful girl.