Hi Leigh, welcome to the site.

Exactly the same situation my wife went through - totally fearless as a pillion, but hated actually being the rider so didn't carry on learning. She has no problem riding horses (or falling off), but could not get comfortable with controlling a bike.

Personally I think she's just happy being a backseat driver/rider (We no longer have the intercom fitted - told her I've lost the chargers!)