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I'm a cat owner and also have also had to bring in a roommate. My cat was dumped outside my house, I tamed her, raised her and love her. She's not much for people in general so I know exactly how she should be treated. The LW no doubt knows this too and while you *might* say she's being a tad obsessive I understand completely where she's coming from. You don't invest so much time and emotion into something to have someone else treat it frivolously and ignore your wishes as to its care.
There are also other things that have to be taken into account. In any 'moving in' situation there would have to have been full disclosure of the cats before the moving. Since all parties accept the cats the owner has the right to expect a minimum standard of treatment of them (that really should be set out before the date - LW maybe your bad there?). I had a roommate move into my flat once who knew how I treasured my cat and how she had to be treated due to her rough start. One night she was standing outside his door and I heard him tell her to move or he'd 'kick her to death.' Needless to say he was gone the next day. Even in jest *nobody* has the right to treat your animal contrary to how you want. The LW can certainly dictate how she wants her cat treated but if it wasn't set out beforehand she'll really have to finesse the situation so it doesn't blow up. And maybe think twice about a roommate in the future? I would rather be a little poorer each week than worry about my beloved pet.