I never assume how to spell
Hayley, although in my mind I always see
Hailey as that is my favourite spelling. My niece's name is Haileigh, and her name is forever spelt wrong.
In her class (she was in senior kindergarten), there is herself and a
Hailey.
I couldn't choose between
Hayley and
Kayley, personally, as that's my niece's name, and also, my son's name is
Casey and I think
Casey and
Kayley are far too close. Having said that,
Kaley would be my first choice.
My favourite spellings are
Hailey and
Kaley.