POOR LIVVY.... AND CASSY TOO!!
I think Karen is right. I would give her a little more time... (and lots of treats and games and toys )
This guy I used to work with took his cat Maggie to the vet and when he got home Patty ( the other cat) was hissin and spittin on her too for like a week or so. I think she just needs a little bit longer to settle down and stop holdin her grudge ..
Maybe give them both a bath THAT SOUNDS LIKE FUN HUH!!
Then she will be real mad but they will both smell the same
GOOD LUCK......... keep us posted!!