I really, really want to like Cathy because Melanie Hill is such a fantastic actress but the writing isn't helping her.
They need to get her out of the cafe, and mix with the locals. Hayley worked so well because of her interactions at the factory etc. She dragged Roy into the community, and the community rallied around him following her death. Whereas it is Roy that drags Cathy into the community.
It just doesn't work at the moment. Give her a new job out of the cafe, give her some friends maybe Gail who is also crying out for some friends and lets see her vulnerability instead of her bitting peoples heads off all the time. And lets see her and Roy have fun, and do things as a couple. Show the love between them.