White cats are particularly vulnerable to sunburn because their fur has no pigmentation (melanin) which is why it is white. The lack of pigmentation reduces the protective properties of the fur. The parts of the cat's anatomy where the fur is particularly thin are the ear flaps. They are also in the direct glare of the sun at a 90° angle to it. This ensures the sun's rays have maximum burning effect.
Cats are not aware that their ears are getting sunburned. The problem can become very severe to the point where the only option is for the ears to be amputated. Removal of badly sunburned ears removes the risk of skin cancer. Cats Protection in North Ayrshire is now looking after her. She looks a bit odd. I like that. It makes her special. She deserves a nice home and some shaded resting places.