Is it normal my new cat is scared of the dog?

My old cat and dog got along pretty well most times. Not besties but rarely fought.
After my kitty passed I got a 1 yo female cat, super friendly with people but she seems scared of my small dog. If dog gets close she will hiss sometimes hide. Shes in the cellar atm, dog is mostly upstairs.
Its only been 3 days how long might it take before shes not scared? And any tips?