Hi IsItHerOrIsItMe,
I don't think SET, or JADE or any of the other tools mentioned here really help. Is it just acceptance, knowing I'll hear about it later ("we always do what you want to do" or is there some techniques to help her express what she'd like?
she is struggling with making decisions. That is human and in some sense pwBPD are super human

I don't think SET, or JADE or any of the other tools mentioned here really help. Is it just acceptance, knowing I'll hear about it later ("we always do what you want to do" or is there some techniques to help her express what she'd like?
There are different ways to improve the situation somewhat. The way you go about i.e. asking her straight seems to stress her too much and then her mind blanks and she gets into defensive mode.
1) Validation.
- Validate difficulty decision making. "Hard time to make up your mind", "Sometimes we don't know what to do / whats best"
- Validate insecurity "Not certain what is best"
- Validate fear "I'm afraid my ideas is not great" <- make it about yourself to not be seen as attacking
-... .
2) Boundaries
- Boundary: "I will not run after her"
- ... .
3) Leadership
- Boundary: "If I'm forced making a decision that if good for me and she does not like it and brings not an alternative I do my thing and will not run after her. My decisions can be reconsidered but in principle they are decisions.".
- ... .
Basically pwBPD have a weak self. That needs strengthening. Boundaries are part of the solution in many ways. This includes sometimes protecting boundaries (see definition of boundaries and how to protect limits) and sometimes simply making sure she does what she is supposed to do and we stay out of it (fighting our co-dependent instincts). This means sometimes acting as a role model and leading the way. This means validating insecurity, fear of judgment etc... This means withholding judgement where reasonably possible and listening actively.
It is a learning process. It would be great if there was a shortcut to it by simply "getting it". Changing fundamental behavior takes time.