Reading back on your post Ebza, it seems some of what your horse is doing is an emotional response. Also when you are a bit uptight ..... which is probably what is happening when she gets a bit emotional, you probably shorten the reins & hang on tighter ......which would actually stress your horse more.
As Saltriver mentioned .....maybe your feel & timing are out, however there are very few people, if any who have a natural sense of feel & timing .....it is learn't over time & with practise & it is not learn't in one lesson.
Steve Brady once said to me, if I could teach F & T in one lesson I would be out of a job
You can practise your co -ordination for manouvers on the ground. So if you were going to bend your horse into a one rein stop position, you can practise this on the ground, with out your horse. Then practise it on your horse at stand still. Practise bending her head & then appling leg to move the HQ. Take the leg off but maintain the bend & when the feet stop moving & she is relaxed, release the bend. Do it both sides & do it in an arena at halt & walk.
This way she & you will have learn't the manouver before ever needing to try it when out.
When you are trail riding, find her position of comfort.....ie at the front. Then ask her to ride beside another horse for a while & then move her back into her position of comfort (POC) again ....so she relaxes. Put the pressure on a little bit at a time & try & relax.....talking, whistling or singing is good .....can't do that & not breath LOL. If you increase the pressure slowly & put her back to her POC, she will adjust to new things better & soon accept it. Then you try something else .....make her walk behind etc.
One step at a time & give her time to think & relax between each step.
If you can have a couple of lessons with someone to make sure you are doing it right, it would be good.
Karen Nicoletto is in Perth & very good with young horse training. I am sure she could point you in the right direction. Make sure your position is good, you are putting your rein in the right spot, you are disengaging the HQ correctly & will tell you the right time to move her forward.
This way you can learn feel & timing

It will also be a cheaper option then sending her to a trainer for some weeks & then having lessons your self.
Seek help now, while the issue is not huge & you will be fine
Anyway there are a number of people in Perth who a qualified to help you get through this. Good luck
