Catnip or the odour of peppermint oil will often calm a cat down. The reason she dislikes brushing is because she associates it with painfull deknotting. Sometimes a shampoo (use a cat shampoo) can loosen the knots, also using a pure, neutral vegetable oil to help condition the coat can be useful....but if her coat is in a very bad way, just trim her all over with a beard trimmer, preferrably just before the spring moult then get into a regular routine of grooming using a grooming glove rather than a brush. This sounds drastic but is often the best and kindest way to deal with heavy matting, as it gives you a fresh start. If you do this, make sure she keeps warm till she is used to her new attire.
Tips for handling irate cats: use gardening gauntlets, or Wrap the cat, that is roll all the unwanted portions of cat snugly in a towel, leaving only the working area exposed. Provided you do not restrict the breathing, and do not go on for too long it will do no harm, and a bribe of food afterwards should soothe the feline temper tantrum that ensues.