I am so very sorry for your loss. Grieving is a very individual thing. It is devastating to lose a furry child. I too, lost a 17 year old fur baby. This was in 2007 and I still miss him and think about him all the time. I can tell you what I did that helped a little.
I went to a kill shelter and saved two cats that would have been PTS. You can never replace a pet you lost but you can love another cat. I knew my Alex would want another cat to have an awesome home, like he did. It helped me to save another life.
However, everyone is different and you may not be ready to welcome another pet as of yet.
Try to remember the good times and all the love you shared with Stella. She is now on the rainbow bridge waiting for you.
If she could send you a message she would ask you to not be sad. She loves you as much as you love her.
There are pet loss grief help sites on there as well:
Sometimes it helps to talk to people who have been through a similar loss. They understand that Stella was not just a pet.........she was your furry child.
If you would like to talk to me anytime, please do not hesitate to write. I can call you if you like.