If she's not resisting milking, only coming through the gate, then I'd look at feet and surfaces, cold drafts where you milk her, that sort of thing - something environmental that she doesn't like. Maybe flies in the parlour? Do you leave her standing tied up while you process the milk or anything that she doesn't like? Does she have to walk across grit or gravel?
And yes, if you're feeding concentrates while milking and she still won't come in, then there's some powerful disincentive there.