I don't think
Jade was ever used by the upper-class here in Australia. Ever.
Christie/Kristy/Kristi/Crysti etc as a full name is pretty restricted to the lower classes here I think. But it's hard to say- I am sure there are those from wealthier backgrounds named
Christine,
Christina or
Kristin that go by
Kristy occasionally...
I don't think
Kristy has ever been overly popular here at all though