I remember you writing much the same things before Dressagegirl.
Sadly it doesn't sound like much has changed in your situation.
As long as mom & dad are driving you to lessons and paying for them, even if it is some of the lesson cost they pay for then their money they get to decide where it shall get spent too.
It isn't right, but it is what it is if you want to ride.
So, show this post to dad to read...maybe it will help if he understands a bit more about being a therapeutic riding instructor..
I don't think your dad quite understands that for you to ride as you do on therapy horses is very different than riding on a lesson horse at a program of "normal" riders and extremely different than to ride a private horse who is not trained to accept the disabled rider...
It makes a difference that the horses you ride are specially trained and exposed to stimuli that most horses would freak out about those specially trained animals not blink an eye = a very big safety issue for you.
The one barn sounds to have issues with leadership and management and I too would not want to be riding their either. Why can your mom not continue to take you to lessons where you want to go to?
If she would do that, then you no longer need to ride at the other.
Not having enough lessons horses is not your problem if you have a set lesson day and time scheduled... Then the barn has a horse assigned for you to ride.
Riding where you question how you are treated is not a place that instills faith in your abilities either...so I see no reason to go nor spend money their either...
Save what you would spend at the place you wish to leave and use it to cut the cost of the more expensive barn and let dad know you are giving up willingly the lessons every month at the barn you don't want to associate with so you can ride where you feel wanted and safe...you don't feel safe nor wanted as a student in the other barn and do not want to return to it anymore.
Because the girlfriend has a horse or thinks she can teach is far different than teaching the challenged rider as you are.
Unless she is a certified riding instructor/coach by PATH and now PATH International then you don't know if she is trained to actually teach the disabled, without that...
Because the girlfriend rides herself does not mean she can teach...and teach you safely so you progress in abilities.
If you want to show and your instructor is not working for a PATH International accredited barn and she is not certified you may not qualify or be allowed to compete as the entry forms must be signed by a accredited/certified coach/instructor...
The biggest reason not to be forced to ride with the girlfriend nor on her horse is you don't feel safe...and feeling safe
on a 1000 pound animal is the first part of being safe.