WIBTA for taking my sisters cat with me?

I was reading another post on here about a brother adopting out his brothers dog after it was neglected and it made me question something I was planning on doing for a few months now. So my sister (25f) has a 6 year old cat who while not friendly by any means, does keep to herself and isn’t very problematic at all. Now the issue is that my sister moved out almost a year ago if not longer. But she left her three cats behind. I adopted one and eventually ended up caring for the second one as well which I didn’t mind because I already had a ton of cats myself so 2 more wasn’t gonna make a difference to me as long as I had the money which I did. Now the thing is that I am also moving in June this year and while I am taking the first 2 with me, Im considering bringing the 6 year old with me too. My sister keeps saying she’s going to come pick her up but the poor thing hasn’t seen her in months. The cat isn’t very nice to anyone and I really think it’s because she either has attachment or abandonment issues. My sister has ditched her twice within those 6 years but will go on her socials talking about how much she loves her. Like I said the cat doesn’t like me but I don’t mind that I just want her to be somewhere where she will be taken care of. Im moving to a much bigger house with a yard where they can sunbathe and play all they want (after chipping, shots and spay/neuter of course) But I know my sister is going to throw a tantrum about it and I could get in legal trouble. She’s not chipped or anything so she’s not really in her name but it still doesn’t feel like I can just get away with it. So WIBTA if I just took her cat with me? Or should I leave her because she’s not my property?