Mod note: Part 1 of this thread reached the post limit and was locked. It is located here: https://bpdfamily.com/message_board/index.php?topic=337479.0An update...
mom's love was full of strings and conditions and threats (FOG) and dad's love was unconditional...they knew he would love them no matter what but not so with their mother.
mom was so enmeshed, and equally emotionally undeveloped, that it was more two kids than an adult + teen trying to figure things out.
Could be typical teenage "your not the boss of me" kinds of things, could be depression and the lack of energy that comes with that or a little of each or maybe her mom is using some FOG on her.
I wanted to re-establish the above quotes from before, because they all confirm that yes, bpd mom has, indeed, has been 'working on' SD16 all this time, contributing to, influencing, interfering and messing with her. I have proof of it. I'm convinced that it's been going on longer than I care to know, especially leading up to summer holidays. Was it to make sure that D did not abandon her and visit her dad and I? sure, but that's just the tip of the iceberg.
SD16 asked to meet with her 'aunt' (our longtime friend - who's also a registered counsellor/family T). They met up last night and went out for a meal together after SD16 got off work (she just started her new summer job at a pub). H hasn't had any contact from D for over a month except a short blunt text announcing that "I have a job".
H got the text today from friend telling him that 'D is confused and depressed' confirming that pwbpd (D's mom) has 'been working on her'. We don't know exactly word for word or the specifics (yet) but needless to say, during the meeting/meal last night, SD was
getting texts from her mother. 
We assumed my SS14 went along because our friend told us the other day that he wanted to come, but we find out today that he didn't, confirming that, somehow, mom stuck a knife in his plan and most likely (guilt) talked him out of it. (Mom also messes with him making it to his guitar lessons btw, that dad pays for, so this isn't surprising). This doesn't shock me, but this is just like the 'drive by' she did a year ago when H tried to meet up with the kids once for a coffee date between visits. The kids never asked to meet again after that. They are teens, and this is just beyond comprehension how much their mother controls everything.
Our friend also said in the text: 'she knows that you (H) have contempt for her mother' (duh), of course these kids know that (we never discuss her), but you know what? H has never and I do mean n-e-v-e-r, has put down, discussed, mentioned their mother to the kids in any negative way, at all. So...this (knowledge of contempt) comes from their mother, confirming to kids (via her 'victim' thinking) how 'bad' dad is for having contempt for her. OMG the frustration. So yes, ruling out of FOG is THE number one fact that I can prove is happening, no longer just an assumption.
H needs time to process. We both don't trust D. I know she's hurting and yes, H might at some point will reach out to her. But I wanted to ask how you deal with or what happens when you establish contact again with D with a highly dysregulated mom being a complete nightmare with her FOG happening at her house ruling with such dictatorship over D. (SS seems okay, although he's highly aware that his sister is having issues with H). On the plus side, we like the peace and quiet and quite frankly we don't miss having D here when she was so completely miserable this past school year even before this mess started. I know that's awful to say that but that's how H feels and I have to agree it's true. D was not communicating bottling up and H could not get her to open up to him. Now I'm convinced D just could not admit to H what her mother was saying or behaving like.
H will have to decide how and what he's going to deal with reconnecting with D. He told our friend that 'she doesn't answer me' (his texts). This is his response to friend saying to him: "She (D) has noticed (this past month) that you (H) haven't been texting" OMG...this is so frustrating. It's like the D has now taken on the victim mentality like her mother. (He hates me and I have absolutely no idea WHY I'm being punished - nonsense). Good grief.
So in conclusion, yes, our kids' (pwbpd) mother is, in fact, indeed ruling them, particularly SD16, by FOG. That yes, since H let the kids decide when they'd like to visit us over the summer, that their mumsy dearest has 'been working on' D which, explains her distant, odd (not like her) behaviour (over this entire past school year prior to holidays), towards her father. And, I'm convinced the pressure as a result has contributed to D's having ongoing depression. We don't know if D has followed up with her Dr. or not but wouldn't be surprised if mom has interfered with that. D is 16 and able to go independently however she needs constant reinforcement to do so. As far as we do know, D has possibly seen her T again, according to our friend.
What I'd like to get help with is: if and when H establishes contact with D again, what that dialogue is going to look like. Quite frankly I'm hoping that it's going to be honest, open and factual which means, that finally, or for once, H is going to have to discuss her mother with D. Of course she is welcome here however since we know to what lengths D will 'obey' her mom and treat dad like

the trust is severely compromised and extremely hard on both of us. Even though we know her mother is behind this mess, it's emotionally complicated to open the arms up to her (which is exactly what mom is messing with and wants). So how do you move forward from this? The one thing that I've always thought that couldn't be messed with by mom is our bond with the kids. Now I know that isn't true anymore and that mom is capable of just about anything and will stoop to such levels I didn't anticipate.