I was reading up on these about a year ago.
You should let her get used to the harness without the lead.
After this attach the lead and let her go around with that for a while. eventually she should let you hold the leash but you follow her direction All being well she should then let you guide her around.

Hope this helps.

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The lesson a kitten learns early in life is:
When you fall off,
over,through or out of anything,
look as though it was intentional.