Moping Dog- Lonely or Sick?

Yes she should be seen by the vet if she has congestion. It could be the beginning stages of an upper respiratory infection, or something else. The reason she isn't eating and drinking is probably because she misses her owners. It's better to be safe then sorry and taking her to the vet wouldn't hurt. As far as checking for her fever, the only accurate way to tell is by taking her temperature.