Hi and welcome to COL
I'm a raw feeder, although not prey model, and feed my two Cockers about 2.5% of their bodyweight, but that includes some blitzed raw veggies and fruit, so the meat and bone content is actually more like 2.1 or 2.2%. I feed around 80% muscle meat, 10% offal and 10% bone using a variety of meats and some fish.
My two are both show type males, both up to height for the breed standard and each weigh about 13.5 kg. They are active, slim and fit. The breed standard for Cocker bitches states shoulder height 15 - 15.5 inches and weight (dogs and bitches) 13 - 14.5 kg. So if Daisy is the breed standard height and average build I think I'd be aiming for around 13 kg. That's only a guess though, not knowing how tall Daisy is or what sort of build. There are plenty of show type Cockers around that are smaller than standard and a few that are larger too.
But if Daisy is breed standard height and build I think I'd start her off on 2.5% of 13 kg and see how she goes. Steady weight loss is better than rapid and I'm assuming that the vet has given Daisy a clean bill of health apart from her weight?
Have you switched an adult kibble fed dog to raw before? Apologies if you have and already know how to. My older Cocker made the transition by having 1 kibble meal and 1 raw meal a day for a while, but some just make the switch in one go. I think if I were to do it again with an adult I'd do it in one go but still stick to two meals per day.
Hope this helps