How is her obedience?
The 2 most important commands are "Leave it" with a long "down stay". If possible working with "threshold" tolerance, perhaps a glass door or gate the cat off in a separate room and have the dog at the furthest part of the room. Whatever food treat you use it has to be the dogs highest value, for Kiya it is liver brownies. I just say "moma's making brownies" and they get excited. It's also helpful if the cat at least learns to be dog "savy". We taught the kitten to stay up high counter tops, the back of the couch, eventually he was able to walk freely but it took almost 6 months for Kiya to chill out. I remember when I tried keeping her on leash while the kitty walked on the floor and she would just turn into a raving lunatic barking and lunging at the kitten. The muzzle was no better with her, as soon as the kitten was close she'd try to bite him. When I started letting her sniff the kitten while he was on the counter (knowing she couldn't jump up there) she'd try to nip his paw, as stupid as it was I had my hand by her mouth, I know she would not bite me.
We adopted the kitten from the pound, then poor kitten still had to live in the dog crate at least when Kiya was around, we kept telling him don't worry it will get better.
You may never get the dog to be safe with the cat, only you can determine that. I did not give up and I was determined to make it work and it took almost 6 months. I still would never trust the dogs and cats alone unsupervised, no way.
Lakota - WGSD 1/13/10
Wolfen - WGSD 12/31/14
Bull -WGSD 2-10-10
Apache - Shiloh Shepherd 12/15/02 - 6/9/15
Kiya - Shiloh Shepherd 5/15/04 -12/19/25