I'm not sure if this issue resolved or not but it sounds to me like your daughter might have PANDAS - pediatric autoimmune neuropsychiatric disorder associated with streptococcus (or called PANS now because they found associations with other infections too). Our son has it. Please research it. It is a neurological disorder that basically causes a hyperactive immune response which causes OCD. It can be treated! Please, please research it online. Good luck and God Bless!
first of all, shes only 6... I was a stepmother for over 21yrs before I divorced her dad. Its a thankless job, theres no doubt about it. You are loving someone elses child, unconditionally and in my case anyways, she acted one way with me and completely different with her dad and his side of the family. She made me look as if I was crazy. When I first met her, I was the best thing since apple pie, but when she realized I wasnt going anywhere, my shiny tarnish started wearing off... You have to remember though, she is only 6 and they do things to get your attention. It seems like she has an honest love for you the way you have told your stories about her and her mother, although you should never let her talk poorly about a parent, especially the one not living there with you (mom). It just causes problems down the road between everyone and it will hurt your relationship with her later on when she does smarten up and learns to think for herself and develops a relationship with her mom. Girls are tough, I have two boys and a girl and my boys were so easy to raise and Im not sure if it was because my daughter was only 6-7 when she found out about her dad being unfaithful and used her to see the other woman but its changed her incredibly. Shes disrespectful and rude and you would think it would be geared towards her dad but its not, its towards me and my mom. She also just turned 17, so we both know how hard it is being a teenage girl... I wish I could say it will get easier but I dont know your girls personality and I will say some of my friends do have lovely girls and Im extremely jealous but their living situation is completely different also. Just be supportive of her, dont give up and please dont take anything out on a 6yr old. Trust me it will strain your relationship with your boyfriend and any other family members he may have nearby, trust me on that! Talk to her one on one and ask her why she did what she did, tell her you arent angry for giving it to her GG and youd just wished shed told her that from the beginning so the two of you hadnt wasted so much time looking for it. If she wanted to go on an adventure together, you could find another way to have fun! I wish you all the luck and have fun with her, they do grow up amazingly fast. Thats something I lever took true to heart and now my youngest son just turned 22 a few days ago and my girl 17, 9 days before that. Id kill for all of them to be little again....
It sounds to me like she has some paranoia. I went through about three or four years of this as a kid. Every single day I was paranoid about everything. Literally. It caused a lot of stress and family problems. Later was diagnosed with OCD and bipolar disorder so I would get a mental health assessment asap so she doesn't suffer.
She seems like she is very paranoid I see you have tried to sit down and talk to her, but if things do not start to clear up you could schedule an appointment with a school counselor or even a professional counselor for her. Second there might be a bigger problem that she might be scared or afraid to tell you.
Similar thing happened to me. It wasnt a deployment, but I had cancer from age 4-9 and was always missing a lot of school due to illness and treatment. I remember in 1st grade I was so afraid of asking my teacher a question, I didnt even ask to go to the bathroom and I wet myself. Stress from cancer, bullying because I was balf, my dad was between jobs and my mother was constantly in and out of the hospital from type 1/childhood diabetes - they may be adult problems but children understand more than we think. They, and many adults, struggle with the stress. I agree making a strong relationship with the teacher and school so they understand the situation. But I most certainly think a councilor will help at lest set a good foundation to help her understand what shes dealing with... Best of luck to you and your family and thank you for your service!
I did something similar when I was a child. I learned what Hell was in church, and I was afraid if I didn't confess everything I would go to Hell. It was a real fear for a long time. I felt damned. As a child, that is very traumatic.