net, I'm sorry to say this but it sounds to me, as an outsider, as if your partner is in some way trying to keep "in" with her parents because she upset them in announcing her sexuality, and she needs to keep showing them that she's still their daughter. Shout me down if I am wrong but I feel that she's is on a guilt trip and wants to keep all of you happy - which is just not possible.
She knows your clinical condition and that you need to keep toxic people out of your life - she has to accept this as part of you as her other half, hard though it may be.
If she won't and she insists that you drive her to her parents - which is selfish in itself - then you don't have to see them, book yourself into a B&B and stay elsewhere.
I'm afraid that she has to grit her teeth with the 10-hour coach journey otherwise -we have to do it when we visit my MIL in Scotland, it's not the end of the world.
I feel some sympathy for her, being piggy in the middle, with manipulative parents, but she is an adult woman and has to made a stand. It may be that she has to choose. If they want to visit you - go away for the weekend. It may look rude, but you've nothing to lose, if you are to keep well.
I hope this doesn't sound harsh, but you have to put your foot down, your own health has to come first.