Both Vicks or eucalyptus oil are toxic to snakes & should NEVER be used in or on them in ANY way. I'm very glad you asked, & it's far better to wait for your vet to see her than to do the absolute wrong thing in the meantime. She isn't even that sick yet, according to your description- just keep her safe at home until you see the vet.
What are the temps. in her home, & how are you measuring them? Sometimes a minimal (2-3*) bump up of the warmth will help, but I hesitate to even suggest that, not knowing what temps. she's already being kept at, because if she's already at the maximum temperature for safety, that's just not an option.