Yearling help

[DDSLYONS@aol.com]

I have an 18 month old filly that I am having a bit of difficulty with and 
would like some training input. This filly is very confident, almost overly 
so. 90% of the time she is wonderful. The problem is when she gets excited. 
She is a class A fit thrower and this seems to be getting worse. She isn't 
afraid of anything and is very dominant. When something sets her off  I can 
barely lead her, she rears and almost runs me over. I'm not a novice and she 
is doing very good in round pen work, and is also is learning to pull a cart. 
She leads great when her brain is engaged. Any suggestions?