Sounds like all she is missing is the drive gear! LOL! If you have her well broke for haltering and leading, then its a matter of practicing and encouraging them to drive. Theres tons of ways to get them to get that forward gear on line going.
One soft technique I use for babies to move out on command under lead, is while practicing leading and its time to step out and up a speed, I will carry a short crop in my opposite had of lead. Subtle and rythmatic verbal cues followed by soft tapping of the crop on their hind quarters. Of course the crop will be held rearward for that tap. They dont expect something to touch them on their hind quarters because all they see is you on lead and ahead. That sudden touch (literally) will startle them and move them forward at a faster pace. Always follow with praise! Practice this enough times and they will get it!
Make sure to work on the feet being picked up. Very improtant along with mouth being messed with and ears being messed with. Touch the udder area as well. It will help with desensatization. Those are sensative areas to babies!
Dixon's Red Hot Ember