My two boys 9 & 13 live here part time (when they are not with their BM) they are talkative, upbeat and "zaney" 

....but the SD18 is here full time. 

Her loser (substance abuse) dad doesn't pay towards anything for her (neither do his parents)

She is pretty much a "shut in" she talks in whisper to her mother  and barely talks to me. She sleeps til 3pm in the afternoon. 

She's been offered but doesn't go to therapy for her anxiety and depression. 

Hi all, this is my very first post and it is meant to be part rant and part plea for some advice/support! 
My OH and I have been together just under 2 years. We made the decision to move in together during lockdown as we did not want to be apart for significant periods during the original lockdown.

Hello StepTalkers!  It's been a couple of months since I posted and I hope you're all doing well.  I suppose I took a little break from venting here because I was trying to make a grand effort to stay on the positive with my relationship with Mr. Ed and completely disengage from SDs, ya know?  But...I woke up this morning with so much resentment, frustration, and anxiety about this situation and I knew exactly where to go for support and clarity.  In advance, thank you so much for this space and the experience you all bring to it!

Where We Were

My SO's daughter, 10, has ADD and a lot of anxiety and it has taken us a full year to wean her off of spending any part of the night needing our comfort. We got her a sound machine for ambient noise and previously we (my SO or I) would have to sit on the floor in her room until she falls asleep, or she would start the night falling next to us on the couch and we'd carry her to bed, etc. We worked really hard on meditation and techniques to help her fall asleep on her own. We got down to a pretty good routine of my s.o.