My daughter is not a good friend.

My daughter will be 8 next month and is in the second grade. She splits her week between my house (where it is just me, my husband, and her) and her dad's house (where it is her dad, his wife, and their 9 month old son).Full disclosure: I had her at 18. Her dad and I never REALLY lived together after she was born. Maybe a couple months when she was just over 1? It's a complicated story but for essentially as long as DD has known, we've been split and civil so it's always been her life. I was also in college for the first 6 years of her life and was basically always stressed and tired, as well as dealing with my own depression and anxiety. I wasn't the best mom, certainly, but have been working on that recently through spending time with her, being more physically affectionate (she likes to cuddle) and trying to share her interests. We also have put her in sports and extracurricular activities (only one at a time, so like in spring she would do soccer and then choir in winter).All that was just to establish that, despite the fact that her parents are divorced, I've tried to do whatever I can to provide for her (getting degrees and then a good, stable job), support her (reinforcing ideas that she can do whatever she wants and she should always stand up for herself and always believe in herself) and engage her (activities she likes). I thought I was giving her as stable and as good a life as I could. However, I'm afraid that I failed.I love her to death, and I think that 80% of the time she is a great, intelligent, funny, creative girl. She wants to be an aeronautical engineer! She makes great jokes! But that remaining 20%? That's awful. It is attitude-filled disrespect, meanness, and entitlement. That 20% was all that was there when her best friend (since they were 2.5!) slept over last night. DD ignored her friend, whined at us about not wanting to do what the friend wanted, and constantly complained. The 20% feels like it's growing no matter what I do.I've asked her a million times about how she feels, what is going on. I've tried to give her tools like writing in a diary, meditation, deep breaths, time outs...I have an MA in teaching so I know how to deal with kids her age, but DD proves impervious to nearly everything I suggest or try to equip her with. Her dad doesn't want her to see a therapist or anything which I've suggested. I try so hard not to yell, I try to talk with her, I try to avoid grounding. But after her behavior last night, I did yell. I did ground her. I made her write a note to her friend and to us. My husband agreed it was what should happen. But tomorrow will come and new challenges and issues will arise.I don't know what to do. I don't know what I need from you all. I guess...am I alone? Are all 8 yo girls like this? Did I fail? Is the damage from being the kid of a teen mom irreparable? Am I approaching this wrong? Am I a shitty mother? via /r/Parenting http://bit.ly/2G25G9n