I had a mother daughter pair and they were ok being separated, etc. Just make sure you DO it consistently and you'll be fine.

I thought of something you can do before she is ready to ride-- have you tried ground driving? That is when you take long lines and teach the horse how to be driven in front of you. YOu can teach the basics of steerign and stopping and going all while walking behind her. It's very fun once they get the hang of it. Then you can walk her down the road and go exploring if she is brave enough...