Maybe she lent it to gma, then afterwards realized she was scared that you would get mad at her for it, so she pretended she didn't know.
Now that she lied, she is probably more confused and might have a hard time processing how to fix it with you, again.
She's 6 so just let it go. Kids do stupid things and don't think like adults do. She comes form a broken home remember. I think two things happened here: 1. She wanted your company. 2. She thought you'll get angry if you found out she gave it away. Or maybe she asked you for the conditioner to gauge your reaction and then got carried away with it.
This child needs love and proper guidance. You can sit down with her and tell her that you know the truth, that you love her no matter what and you forgive her, but in the future you'll want the truth from her. Build up trust and don't spend your time feeling upset over the actions of a small child from a broken family.
You are not alone unfortunately! My now husband and I started dating when my step daughter was 6. Her mother dropped from her life after minimal visits. She is now almost 12 and it has been HELL for almost 6 years now. MANIPULATION is not a strong enough word. Everyone tells me that she is angry and testing me to see if I will leave too. She is STILL constantly bringing up when it it was "just me and Dad" which was about 3 months! Nothing we do as a family is ever good enough, yet she hugs me and says I love you cinstantly. Please see a good family therapist ASAP dont wait like I did!
You have lost all love for this kid over a lie? It sounds to me like she is extremely desperate for attention. Kids don't differentiate between good and bad attention. Attention is attention, and kids who are seeking it will sometimes enjoy negative attention more than the positive. Does she get any real attention from either of her parents? I'm guessing that either you are at your wits end because of some horrendous thing that you failed to tell us about, or she's seeking attention (any kind) that she's not getting, as she seems to be surrounded by family members who are ready to throw in the towel on loving her over a bottle of shampoo
I think a little family therapy is needed here, and some parenting groups for blended families. She was abandon by Biomom, that alone could cause long term behavioral problems, Daddy is now splitting his attention w/ her and you. Her emotions are all over the place. If you no longer can stand to be around her and shes only 6. I don't see a happy future for any of you. Get some professional advice before its too late. She lost 1 mother, next one doesnt look too promising either.
Her mother has rejected her and she's afraid that you'll reject her too. That's why she's overly sweet, lies because she's afraid that the truth will push you away. Why she is giving things away it's so that ppl will like her. She just wants to be wanted & liked, so she lies & "manipulates". Many hugs.