If I can help talk you off the ledge a teeny bit here.  Please don't take what she is doing (not doing) Personally.  She isn't slacking off.. wasting time with her friend to spite you.  It's really a lot more likely that she has a hard time prioritizing and with immediate gratification.  

I had a similar experience with my YSD when she was 17.  She was a great student.. zero behavior issues.. so responsible.. and she even arranged her remote learning so she could graduate early.. take some college online and go to work.  

But.. follow through? ughhhh.. the snapchat marathons she participated in.. the 4 week class that turned into months.. the finding "anything" to do before her school work.  The "teacher hates me" me trying to follow up with her long distance every day.. log on check her work.. and she was always shining me on about what she had done or left to do.

but.. you know what? that was a super tough dynamic.  She (and we) probably underestimated how isolating that was... and she craved that contact with her friends.. snapchatting and texting away.  This was the first time she was able to "make her own schedule" and she fell into some traps there... and as a teen.. got resentful of my poking her along.

I finally backed off and told her.. look.. you wanted this.. you finish it.. it is up to you.. and she eventually did get it done.  She is now a very successful young professional... and while she can still juggle and procrastinate.. she learned a little about herself in the process.

I think the bigger issue is that neither of her parents are able or willing to pick up the rope.. and you feel morally obligated to do it... and you like her.. feel sorry for her.  I don't blame you.

but... at some point you do have to admit that she is her own person and will need to sink or swim on her own.  Lots of kids are in her exact or worse position right now.  Hopefully when In person resumes.. she will get caught up.. or have to repeat a grade.. worse things have happened.  

14-year-old girls are fairly rotten human beings; but it's not abnormal for her to want to spend more time with her friend than on school work.

Honestly, it doesn't really work to manage a kid's school, even with your bio kid, and definitely not with your stepkid that has two parents who do bupkis to help her. 

Can you back off into a civil and pleasant role and no longer try to save Munchkin? Also, why do YOU pay for her phone?

not your circus..not your monkey....repeat after me...not your circus not your monkey.

Your DH needs to handle this..not you.  As much as you love munchin....still not your fight.  If DH can't/won't whatever that is on them...her parents.  You can "help" if you want to but it seems you are more invested that either of her parents.  While it is hard ot watch the impending train wreck..better to be the spectator than being on the tracks with them.

I have been reading your blogs this last year and seeing some parallels with munchkin's struggles with virtual schooling and those of my sd12. I have gone back and forth and helping and not helping. My husband is fairly useless at being consistent and refuses to limit sd's internet useage to help her focus on school work, he also refused to really impose any real consequenses on sd's late work or her low grades (we were sympathetic with the first lot of f's as this is all new etc..etc..).

Over all one of this the most fustrating thing has been sd's sullenness and rudeness when I have been trying to help. SD's attitude was pretty bad and I have blown up at her a few times this year. The last time it was really bad, I managed to get her to apologize to me afterwards (that was tough as she generally fails to do this) and it helped me to feel less resentful towards her. Her attitude has been a bit better since then.

I am ok accepting many things, but I will not accept disrespectful behavior, that is my line in the sand. And when I feel disrespected I feel like you do and just want to throw my hands up and walk away. This year though I have realized that I physically cannot as the urge to help prevent a very capable child fail because her father is unable to be consistent is overwhelming. I have reasoned to myself too that it is helpful to my future if sd does not fail highschool as then hopefully she will launch in a timely manner and go on to lead a self-sustaining lifestyle (unlike her mother).

I also have to keep reminding myself that sd is only 12 and even then she is less mature than I think a lot of 12 year olds are in a lot of ways. I feel that all of the issues with her mother and the divorce have retarted her maturity in someways. She is also limited as to her social interactions right now to online friendships - so I can see the wisdom in ESMODS words above. Plus we have BM telling sd that grades are "only letters and don't matter".

These all contribute to why she is incapable of being responsible for her school work without regular check-ins. Sometimes it is easy to think that she is just being obstinate and difficult, but I have to remind myself that there are many contributing factors to this and try to find some empathy. The empathy is harder to find though when she is being rude towards me and seems to reject my assistance. 

I am thankful though that sd is with us 100% during the school year, this means I don't have to deal with sd regularly falling behind on BM's time like you do.

Sometimes no matter what you do you nature will win over nurture. I learned this with YSD. I thought she would be different than OSD as she was younger and exposed earlier to normalcy.

But I found out it didn't matter. As she nearest 13 she began down the very same road I watched her sister down. Because like you I was the strong alpha presence trying to maintain the rules and boundaries. I became the target. Which is not abnormal for any teen.

The problem lies in having a parent who sees an opportunity to place themselves in the limelight with the child by encouraging, supporting and justifying said teens rebellion. 

That's when your efforts become futile and you are just spinning your wheels because you will not change or accomplish anything.

I'm sorry I can completely understand what you are going through. I think what hurts the most is there is no loyalty from these kids. You think they would at least care enough not to throw you under the bus, but nope they don't and they do every single time.

We went through the same thing with Spawn. Things would appear fine life would be going along and then BAM! Spawn would throw us under the bus about something and Meth Mouth would be on the war path. It also gets harder the older they get because now you know they understand what they are doing, they aren't just kids anymore.