R.W.
Your Daughter sounds like me when I was that age.
In short I had self esteem issues, as well as some depression, and other stuff going on.
I lied about anything that I could lie about for any reason. I even lied about stuff that didn't matter, it was ridiculous!
Wanted to appear better than I felt about myself. Wanted to pass the blame onto someone else, because I didn't want to feel worse about me (which just ended up making me feel worse anyway!) Wanting to Not get in trouble if I could help it.
It wasn't until I was an adult and got into therapy that the self esteem, and Depression were addressed. Honestly one of my big therapy issues was Trust...I didn't trust anyone with the truth...
I hope you and your Daughter figure this out.