My DH's BM occasionally experienced breakups or relationship problems.. and YES.. they can lead to more visibly toxic behavior.

When the kids were young/minors.. it would often result in more sporadic visitation issues.. and also ramping up requests for money.. etc... she also "focused" more of her energy on the kids.. which was not a positive outcome for them.

As adults.. the first time it happened after she was out of a long term relationship was her claiming she was going to go after my DH for spousal support.. never mind that we had been married over 10 years at that point.. and she had cohabitated with her bf for years.  obv she was not entitled... she also wanted my DH to pay for her health insurance.. he said no.. haha.

When single and without a guy to mooch off of.. she also has at times spent more time with her adult daughters.. (again.. not a great thing for them given her nature).. and has mooched off of them .
They are adults now.. we can't stop them from helping their mom.. but when we get whiffs of it happening.. we remind them it isn't their responsibility.

Thanks for the feedback, everyone.
I'm not letting my guard down. We are preparing DH for retirement at the same time, and this newest revelation has me a bit apprehensive on the financial front as well.
DH carries SKs on his insurance, but she also has them on Troll's insurance because she doesn't want DH to see EOBs. This is in spite of the fact she is court ordered to share medical info with joint decision making. We are long distance, so this is easy to do for her and hard for us to prove. 

BM earned some pretty strict boundaries and I'm pretty confident DH won't ever let up on her. She is wily and has always been good at playing the victim. I don't know the details of this possible split, like who initiated it, but I can see her playing double victim now if her troll husband did. DH's son is not equipped to be the proverbial "man" of the house and BM has never EVER been a "strong independent" woman. She has always relied on her parents and then DH and then her next victim the troll. It is giving he left her or maybe they decided on an open marriage. Who knows, I don't really care other than how it may affect us down the line.
She is super secretive so not sure the kids even know. Even if they did, they have been taught at an early age to never talk to dad about anything.
While BM and Troll seem to be living separate lives there is some plausible deniability in a teen's perspective, being too wrapped up in their own world to realize what is happening.