She will learn to cope with it in time, just like I did, but until she realises it isn't real and underneath the costumes and masks there's a person it's going to be pretty much the same. It's a fear, a phobia and she needs lots of reassurance.
Don't change anything, walk past santa with her, let everyone wear masks at halloween etc otherwise she'll never get the idea that it's all pretend, she needs to become familliar with her fear and learn how to overcome it herself.