I've got 2 cats, one older and one younger. The older one we had for 4 years we got her from a rescue and she's really taken with us and we've been really happy since, however we got a new kitten last year and although she wasn't happy initially she came around, but her personality changed. She's generally grumpy and shows displeasure at most things - though she's never aggressive.
However a couple of weeks ago she just left (she rarely goes out) and didn't come home. Only in the middle of the night to eat the dry food and was gone again. Literally for 2 minutes. She did it a few more times then stopped coming altogether. I've collected her from 3 separate neighbours who all say she runs into their house and settles down, and the moment I bring her back she is desperate to leave. She constantly hisses at the kitten but he's the nicest little thing and keeps his distance from her. I've taken to keeping her inside in order to re-introduce her to the home again because maybe she feels she's lost her territory but she just looks miserable. So I don't know what to do. I don't know whether to let her out and watch her disappear, or see if this works and she comes through it to understand this is her home.