I am so very very sorry about Sweetie.

It could also be that Cutie is being visited by Sweetie and she doesn't know how to react.
After my Pumpkin crossed over, my Shadow would watch something in our bedroom and follow this invisible thing al over the room with her eyes. I am convinced that Pumpkin was there.

Animals do come back and visit us an dtheir animal friends just like people do.

Blessings,
Momma cat.. Deb