I would either put up a gate that they can see each other through or put your dog on a leash and have him lie down. Have one person feed the dog treats so he is occupied and let the kitty come up and sniff the dogs back side on her own terms. She will still likely hiss but if you dont push her and you keep the dogs head occupied she should start to calm down. Before taking the dog out of the room move the kitty back, if she is near him when he stands up it will probably scare her.
Most cats will not make friends fast with another animal. When i brouht home a new kitten my current cat hissed and growled for a while. Now they are best friends, cats just dont trust that quickly, just go slow.