the pull to the left is most likely due to crown in the road. Is it a consistent pull or does riding on different roads change the handling? As for the shimmy, check the toe.

Oh yes, one of the disk brakes constantly squeaks ALL the time, and if I adjust it out away from the disk there is not enough to apply the break...how do you get rid of squeaky breaks?

Just a hair bit of toe in should make it more stable. Nuetral makes them wander and toe out makes them wander but turn faster which is not a good thing on a trike. It is a bit of a learning curve with trikes. Death grip on the handles bars makes them feel shaky also but you say she rides with a relaxed grip so not sure on that. If I remember correctly a baseball card is the adjustment you want disc to pad. Put them in there, tighten them up and then roll the cards out. If not maybe you have a warped disc and that would certainly cause it to pull and drag at speeds.

Try a MM of toe in or so and also check the tension on the thing a majiggy that the bar pivots on below the seat. I believe it should have a little bit of tension to it to tighten things up a bit. So many little things though. The reason a say a warped rotor might do it is the fact that it is pulling one way and she is correcting the other. No problem at lower speeds but at high speeds no bueno. When you say high speeds about how fast are we talking. I had my tour up to the 40's and it was sketchy at that speed but after a while it was controlable. Some of it was just my technique and getting use to it but there are alot of things that make it way worse. I can not remember if they sell stabilizers for these things or not.

Breakes squeak if no one is on the trike, or if anyone from Kim on down to my 9YO is on it.  Just sitting with a slight movement it squeaks.  I'll try cleaning and sanding today.
 
Funny thing is the right break is the squeaker, and the trike pulls left!    Will work all the issues this evening...

 Forget toe-in, just align the wheels straight on, since toe-in causes the tires to wear unnaturally and increases rolling resistance, by causing one or both the tires to always drag slightly sideways.  A frequent symptom of toe-in is a side pulling effect.
 
Another contributor to side-pull is having more brakes applied on one side than the other.  This sounds especially appropriate since you mentioned one side squeals frequently.  Loosen the squealy side until it stops squealing.  Don't miss the fact that there is a friction pad on both sides of the disc, and both sides need enough clearance to glide by without dragging or squealing.
 
Another contributor to side-pull is having tighter wheel bearings on one side than the other.  The bearings should be loose enough for the wheel when suspended in the air to rock back and forth until the valve stem settles at the bottom.  You may notice a very slight wheel wobble becomes possible when the bearings are loose enough to spin that freely.