Can Pets See into Different Realms?

I have a Cat about a year and a half old, and lately shes been acting funny, she always seems tense and nervous, she sees things that chase her, that arent really there, and she stares at our closet door for hours, do you think its possible that she could be seeing something that human eyes cant see? something paranormal? does anyone know if animals can see into different realms? i would really appreciate and answers anyone has thanks