The others have given some good advice. I can't add much except that I think you're doing everything you can. Cats are VERY territorial. Sometimes all you can do is keep the less-aggressive one away from the others.
There is a product called Feliway that you can buy at pet stores. It's a synthetic hormone that helps cats to calm down. You can spray it here and there in the house, in the places where she spends most of her time (not directly on the cat). It can be pricey but is usually less expensive if you get the plain bottle...there's a kit that comes with a video but that's the more expensive version. Your vet should be able to tell you about this and might even be able to sell it to you.
She defiintely needs a place to call her own where the other cats won't bother her, and her own litter box and food bowls, if possible placed where the other cats can't get at them.
And I agree that if possible, you might try sitting down with the menfolk and explain that what they are doing is cruel to the cat, and it hurts you as well. Be nice but be firm. If they care for you at all they will at least listen and hopefully change this behavior.
All witches are bit odd. It's best to get your oddness sorted out early. (Terry Pratchett)---
Nothing grows in Midgar.