How did the Birthday party go from you having a "surprise one" to you and her discussing "who" was coming ?

Looks like your insisting that she go into the home for a form has really triggered her in some manner as to cause such a strong reaction. Was there no other choice but to sent her into your home for a "form" Could it not wait for you to retrieve it? or wait for her to stop by while your parents were there to hand it to her?

Maybe she would benefit from seeing a Therapist to find out how to move forward and find out whats caused a strong reaction.

I think you need to be cautious about pushing her to much on this, she "seems" fragile.

I hope things can be worked out.

Welcome to PC