One thing you can do is first ride her bit away, if she starts to be fussy go back and trot her quickly in various circles. Really make her work. Then walk her away again and see if she wants to rest. Just repeat this process. What you can also do is take her for a walk and when you get home work her hard. This will make her think that going back home just means more work and she will decide that she doesn't actually want to go home.
Hope this works.
PS check out www.equisearch.com
and type 'herd bound' or 'barn sour' into the search engine. It will bring up some more articles on this and how to deal with this.