ignore it until next time mode, it can be a better conneciton with blended family peace. If they will keep their heads out of their asses and you do not have to be forced to ignore the resurfacing of behavioral crap from B/M.

My SS used to beg for me to re-take the lead in parenting and discipline when his mom would go into one of her full engagement discipline and parenting phases.

"Dad, can you please go back to disciplining me. You are clear on what I need to do, you apply the consequences, then let me figure it all out until next time I screw up. Mom lectures me incessently, for days and even weeks on end.  Pleeeeaaaassssseeee Dad!"

This would usually occur when she would take exception to how I parented or disciplined in a specific situation.  I would tell her if she did not like how I was parenting/disciplining to step up and get it done before I had to.  So, she would get all in his Cheerios. 

Take care of you CLove.

Only to repeat the cycle.  They don't really deal with anything, eg acknowledge the issue and work towards change.

It isn't unusual in dysfunctional families to bury things and move on.  Not always healthy, though.

I don't know if you have been overthinking or if you just don't operate the same way. Some people are fine with "wiping the slate". Other people aren't.

I think it comes down to what is being wiped clean. A petty fight with no real consequence is probably fine to wipe away. But years of bad parenting? Abuse? Neglect? That can't just be "wiped away". Individual instances might be able to, but the impact of those bigger things linger.

Ultimately you have to decide what you can and can't just wipe clean. An entitled 16 year old who has never been effectively parented acting like a 16 year old who acts like they have never been effectively parented? Yeah, most of that should probably just wash away. Some of the other sh*t that keeps rolling downhill toward you, though?  You'll have to decide whether you can let it go or not. If you can't, that's okay. This just may not be the family dynamic and partnership that is right for you.

As long as you don't take it as some signal for you to wade back in with your version of "helping/doing nice things" for everyone.. then as has been said.. for petty stuff.. minor misunderstandings.. yeah.. just put it behind you.. move on.  But don't mistake their chipper attitudes as a permanent state of mind.  Like everyone.. good days.. bad days.. 

My best advice to you is live YOUR life.  Deal with your SD as needed... mirror what she appears to need at the moment.. whether that be you out of her hair.. or a sympathetic ear.. she will feel like she wants different things at different times.  Let her ask for things vs you pressing her with opportunities and obligations.  Let her parents manage her education.  I don't care if your DH is a computer idiot.  my father is 93 and can manage on a basic level... show him.. and if you have to log on for him.. fine.. but let HIM ask you to help him..   it's not your responsibility to manage and you inserting yourself just opens you up as a target.