I have been reading a lot about narcissists and especially covert narcissists, and the strategies narcs use to manipulate people. And I actually think it has given me some clarity in regards to my interactions with SD20 and how she manages to manipulate so many people in her life, like DH, her doctor, teacher, etc. First of all, everything I read is spot on describing SD behavior. 

So it was eight days of blissful freedom. I enjoyed every minute. Now, SD20 is back. She came running to our house mid-day but forgot her computer, so she had DH drive to BM and get it. After he came back, SD was asking him how it went, and DH said that BM was in a horrible mood and pouting the whole time (sound like SD!). DH said, I do not know why she was like that. SD said yes, I know, I just feel so drained when I am with her (also, sounds like the way SD makes me and DH feel). 

It has been a peaceful and lovely weekend... You guessed it SD20 was not at our house.  I know that I am probally a fool to accept DH behavior regarding SD, but it feels so good just to enjoy the happiness while it lasts.

DH has been so charming, woke me up to breakfast in bed, and was so nice to be around the whole weekend.  We have laughed and had a good time.  

Yikes! I am in so over my head with SD20. She comes as she wishes and stays as long as she wants. She is incredibly spoiled, never worked for anything in her whole life, and has a parasitic mindset. She is now trying to finish high school for the second time. She has this show going on telling everyone she workes all the time(she did this when she had secretly dropped out as well). Even sits there at family dinners saying DH family how she works double what I do (I have two jobs, and she pays nothing for anything other than her own Funtime).