Poor Maggie sounds like she has been struggling with her skin for sometime. Skin disease in cats can be very frustrating for everyone involved. Maggie is scratching her face because she is itchy and with those sharp claws she would be able to do a lot of damage in a short time as evidenced with the bleeding and scabbing you see.
The causes of itchy skin are numerous and often getting to the bottom of the problem takes a methodical approach with elimination trials and tests. Many skin diseases in cats are very treatable but you just need to find out what to treat! I once saw a cat with very similar symptoms to Maggie and it turned out to be ringworm, once this was determined, treatment was very straightforward and the cat’s problem completely cleared up without returning.
There are veterinarians who just specialise in diseases of the skin, they’re called Dermatologists and often a tricky case such as Maggie’s can be very efficiently diagnosed and treated in their hands. I would recommend either revisiting your vet and explaining that you would like the problem looked into further as it keeps recurring or contact your local veterinary dermatologist.
Best of luck!