An unexpected 3rd child

This may turn into a wall of text, so please forgive me...2 yrs ago, my brother and sister in law took in a foster child. She had essentially spent 16 yrs being abused mentally, emotionally and physically by her mom's partner. About 9 months ago, they took permanent guardianship of her as her mother chose the abusive wife over her daughter.The girl took this to mean that they were unofficially adopting her. We did as well. My husband and I had never really gotten close to the other kids they have had, knowing that they would more than likely be leaving at some point. This girl is part of our family now. We treat her like any other of our nieces.Obviously, this girl has some issues. She has been abused and abandoned by everyone who was supposed to love her. I tried explaining to my sister in law that you can't recover from abuse like that in a year. That most people spend their whole life trying to get past this, that it is scientifically proven that emotional abuse physically alters your brain and that tough love doesn't work with a kid that is already expecting you to walk away from them.Well...they got into an argument again with her after they tell her this is the last time they will deal with her outbursts. she said "I'm leaving! I'm 18 and you can't make me stay!" and she went to a friend's house. So knowing her and her pattern of impulsive behavior and the immediate regret that follows her blowing up, I texted her and asked if she wanted to go get coffee and talk. She said yes and then asked " Should I bring my stuff?"..which pretty much told me that she was hoping someone would come and get her. I said yes and she came home with me, which surprised and pissed off my sister and brother-in-law ( apparently we were sticking our nose into their business).My brother and sister in law have decided that they are done with her. They just can't deal with her any longer and they want her gone. My husband and I assure her that she can stay with us until we figure everything out. 3 different foster homes fall through. Her aunt who originally said she would take her, backs out. Her only other option was to get an apartment of her own. My husband and I think this is a terrible idea as due to many of the issues she has, she is more like the maturity level of between 14-16 yrs old even though she is physically 18.I think we have both lost our minds as we have asked her to stay with us. Both of our boys are okay with this ( the 6 yr old moved into our room so she has a space of her own). We know it's not going to be easy... She has ADHD ( like my oldest son along with her outbursts. Her caseworker, although grateful that we are letting her stay, told her not to get too attached to us...in case the same thing happens again. Which totally breaks my heart, because no matter how old you are...you always need to know you belong somewhere. We told her that she is family and she will always have a place with us, no matter what.My brother and sister in law aren't bad people. They do care about her...but I think that they have totally unrealistic expectations of a kid that has been through what she has. They seem to think that a yr and some odd months of living with a "normal" family should fix everything and they don't understand why she just couldn't be "normal". They are angry that we would let her stay( not that they would say anything to us but I overheard a conversation they were having)...I am guessing it is partly because of embarrassment of having to explain that we took her in when people ask why if they don't have her anymore, why she is still in town.Ugh...life is so incredibly complex with twists and turns you could never imagine. I never thought I would end up adding a third child to our family, especially an 18 yr old one. My husband and I aren't well off. Most months we just scrape by, but we couldn't let this girl be on her own. I remember how scary it is to strike out on your own even when you are ready for it.So...yeah...we have kind of lost our minds. Half of our extended family is mad at us for being nosey and the other half is impressed with our generosity. And now we are a family of 5. via /r/Parenting http://ift.tt/2zygQQO