She is still walking
back home, correct?
If so, I don't think you could (or should ) do much about it. I think it is normal for all horses to walk faster going the direction they want to go. Now if she were jigging or trotting, etc. that would be different. But as long as she is walking, I don't see it as an issue? But maybe that's just me.
There are days my mare won't even walk coming home. I have a rule that she can go as fast as she wants as long as it is at a walk. So even if she speed walks home, that's still a walk and I consider it a success.
It may also get better with more trail miles. If I keep my mare well ridden, she walks coming home. If I let her sit for a week or more, I know I will have issues with her not wanting to walk.