Then your issue seems to be more of a “how do I tell my trainer I’m taking my horse for a workup at a clinic and I am not interested in using her recommended vet anymore” and “logistically how do I book someone to take my horse there” which are totally valid questions but different ones than where this thread started. And I’m an assertive type with my own rig so maybe not the best person to answer THESE questions.
Your horse, your bills, your decisions. You don’t need to be rude but you do need to be firm. “Hey trainer, I called Tufts and I have an appointment to take Middleton there on 3/25. I’ll be here to put his shipping wraps on at 9am and I’d appreciate if he can be left in his stall that morning so I don’t have to catch him. Thanks and I’ll update you after the visit.” Not sure you need to get into it more than that. I mean, she’s scared to ride your horse now so why would she be opposed to you drilling down more on the issues? And it’s totally normal for people to haul to a clinic after trying things in the field and finding they didn’t work. If broaching this with her is some sort of groundbreaking development or major problem-- that says a LOT about her (and none of it good). What’s your proposing to do is completely typical horse ownership stuff. Even a really controlling trainer is going to understand that at some point the client wants to take the horse to the clinic. And at the point at which she’s afraid to ride it… what does she gain by OPPOSING this? She didn’t even sell you the horse. If he’s got a problem, it’s not on her. I don’t even understand why she’d balk, even theoretically.
And as for a shipper, does anyone in the barn have a truck/trailer? Who do other people in the barn use when they have to ship places?