My 4yo gelding was real heard bound. I was riding with the horse he was sticking to out on trails and carrying sweeties.. every now and then id push him to go ahead of the other horse and reward him..
Eventually, I could ride in the school without the other horse with sweeties.. and now he's heading out on hacks alone with me for the first time ever! He's on his toes alot, and whinnys so much! But he's good. I don't carry sweets anymore unless im teaching something new. Everything he does good for me now he's rewarded wit a scratch and pat, which I done before and after giving him a sweet.
The idea for this is to have spirit build her confidence with you. At the moment she's probably thinking she's in a bit of danger when being separated from the herd.. do you have a field in sight of the other horses? Id try working with her in there until you feel confident to push her boundaries a little bit more... SLOWLY does it, your building confidence for you and her, it will take time.
For your next big step, take her out around the block for 10-30 mins just walking so she realises she will be coming home. If she speeds up when she realises she's on her way home, slow her down and take her back at her own pace. Even stop her and turn her around for a few steps if she doesnt keep to your speed. Please remember though, as soon as she realises she's heading out on her own, she will more than likely try turn back around, just bear with her, but keep her under control. Don't let her go home. Just keep calm and turn her the direction you wish, then reward when she's doing what you like...
This is exactly what I done with my boy. And I have never noticed such a difference! He's a hell of alot more confident with me, and I am with him! And also because of this he looks forward to being rode to go out and 'see the world', and he's more forward! Which is great because he's just began his education!! So much easier when he's willing to learn !!
.... Ill keep checking back for updates xxx