How can you "help" them get back to baseline sooner?
I explored this back when I was with my BPDxgf, only once did I manage to even come close to what could be called "helping her back to baseline", and it was when she was angry at me for "not caring about her".
I told her I didn't want that to mess up our thing, I sort of "reached out to her", told her in a "tell me what to do" kind of way. She said "fix it then", and I basically love-bombed her for a moment; after that she just said "you did good".
This is one instance of one couple that ended up breaking up a few months later, so its not bulletproof or even "reliable data", but at least in that moment when she wanted to be rescued I sort of asked her to show me the way, it was a cooperative thing, it was "us", a team, "we" got through that.
At least that's what I like to believe.
Am I so cheap that...
My gf said a very similar thing before ghosting me, I thought it meant she didn't want to spend too much money (she had gone out to a bar but was having second thoughts about it) but it was about her low self esteem: she was feeling very, very abandoned at that moment; I paid the price of my mistake with our relationship .
Then again, if their minds are that similar maybe my "fishing her out of dysregulation" anecdote might actually be useful for you