my daughter is disturbing me

I’ve thrown her in therapy but she just seems to antagonise her therapist. I have a 15 year old daughter, and she’s always been defiant and naughty, but she’s just gotten so, so, so bad over the years. She lies and lies all the time, then at 11 she began high school (yr 7) and she just refused to go, would cry, struggle against her dad etc. She’s always been violent especially to her younger brother, but this time she actually started getting a little brave and fighting back against her dad physically (he would pick her up to make her go to school and she’d kick and scream). This went on for a few years. Then she got more silent and sneaky, she still lashes out but.. as teenagers do, they find themselves more and she’s been doing disgusting things. Firstly, she’s cruelly killed multiple of her small pets which horrified me and her siblings, and she kept smiling or laughing whenever I confronted her about it! At first I thought she was smiling as a joke, but her smile was genuine and she couldn’t control it, just any mention and her mouth twitched even if she tried to hide it (which made me feel sick to my stomach in all honesty. I couldn’t even look at her, and she knew it so she kept rubbing it in my face what she’d done) I’ve recently discovered that she has this crush on some German pedophile?? Christian Brueckner I think his name is? And she’s like in love with him. I thought this was all bad, but I’m now discovering that she herself may be a pedophile, or atleast have pedophilic interests because I saw multiple drawings of hers which were quite graphic, and I’ve also read these little rhymes she’s written. She’s also visited I think it’s the dark web (idk, it’s on Tor) and she’s been to questionable sites involving children.. (I reported this, and she got off so easily which is disgusting) I’m beyond disturbed and I don’t know what I’ve done wrong in raising her. I mean there were signs I guess especially this time when her sister (who is about 5 now) was playing in the pool with her. I saw my 15 year old (then 13) kiss her on the mouth and hold her there, at the time I thought it was something sweet but now I doubt it. Sorry for my horrible grammar, I’m a mess while typing this.