It looks like from your previous posts that she is gaslighting you ... you feel x then check with her to see if it's accurate, and she says no, it's y.
No wonder you feel upside down.
She seems to be high on impulsivity, and the self-harm and suicidal ideation is worrying.
When you aren't sure what's real, it's understandable that you're checking her social media accounts. There's probably no point in confronting her because she isn't likely to admit to bad behavior ...
What is S14 and S4's relationship like with her? With you?
Is the father of S14 in his life?
Has your wife weaponized the kids against you previously?
It may work slightly different where you live than here in the US. Once you meet with a mediator, what happens next?
As for her calling you abusive, or weaponizing the kids, or doing anything that undermines security, stability, safety ... I would prepare for the worst and hope for the best while taking excellent care of yourself. From what you have shared here, she is more likely to experience suicidal ideation, risky behaviors, and self harm than other BPD tendencies, although you know her best. If she has already shown signs of weaponizing the kids, or has made threats about false allegations of abuse, those are red flags worth paying attention to. However, just because she is susceptible to these behaviors doesn't mean they will happen. It just means if you have felt tremors and live in earthquake terrain it's worth beefing up your insurance policy to cover structural damage
This is a good site with lots of collective wisdom about navigating these emotionally charged exits. The skills are not intuitive and must be learned, and are useful whether you stay together or decide to end things.
Hang in there. There are lots of people here who understand what you're going through and are willing to walk alongside you.
