Hello there. My name isXXXXX and I am so sorry to hear about Trina. It definitely sounds like Tiger is grieving from the loss of her house mates. Cats definitely grieve and miss their house mates when they leave or pass away. The best way to deal with this is to give her time to grieve. Allow her to remain where she is quiet and do exactly what you have done. move the food water and litter box into that area so she can eat and drink and use the restroom when she feels like it. It can take a few days to a few weeks for some cats. Do not try to force her out of the area at this time and point and do not close that area off. She must be given time to grieve. With that said though i would strongly recommend having her examined just to be a 100% sure nothing else is going on especially since the other was lost at a younger age. Your vet can give her a good physical exam , I would recommend blood work to make sure everything inside is running normally and to do a urinalysis to ensure no abnormalities in her urine. That way you know a 100% that everything is ok with her then let her go back to grieving. I hope that makes sense. But in review she is most likely grieving and will take time to get over the loss but I would be a 100% sure and get her looked at by your vet. Please do not hesitate if you have any further questions or concerns. I would be happy to help. Please do not forget to rate my response so I receive credit for my time. Thank you!