worry that I might say the wrong thing.
you almost certainly will. we all have and will again. try to understand that this will happen. being a safe place for her to go to, and a source of constant love (is precisely what you want to shoot for, and what she needs) doesnt preclude that. its what will sustain your relationship through the storms.
understand that a diagnosis and/or therapy may mean a lot of volatility, even if, initially, there is a sigh of relief for one or both of you. its a journey. things can get worse before they get better, and thats not to say they cant get a whole lot better! its just to encourage you to go into this process with eyes wide open, and youre asking the right questions.
there are (among many others) two good places to start in this process:
https://www.bpdfamily.com/content/what-does-it-take-be-relationshipthis is written for parents but is highly relevant:
https://www.bpdfamily.com/content/support-child-therapyadditionally, its a good idea to have a strong support system yourself. im glad you found us.
how long have you and your wife been married? what led up to her seeing a psychologist and a psychiatrist?