Is Cleo spayed? This may be a symptom of a false pregnancy if she is not.
It sounds awful but the worst thing you can do is try to comfort her when she is upset - if she is missing your Dad.
The best thing you can do is check her teeth, throat and monitor her eating - if all seems fine to you then it is kindest to wait until she is not showing any signs of anxiety and choose these moments for a fuss, or, even better, a game or walk. Try to tire her out when she won't associate your reaction to her showing distress.
If she continues to show distress you must try to ignore it - it sounds awful as she may be really upset - but dogs are very clever and she will learn by your reactions that being noisy and looking sad get her a lot of attention. Pick times to give her extra attention and excersise when there are no whines or toy carrying, both of you will feel better! A tired dog will sleep, not worry. Good luck, try and be strong, this can be harder on owners than the dogs!!