13 year old daughter lying and being disrespectful.

Hello, we have a daughter who will be turning 14 here soon. I am not her real father, her real dad abandoned her shortly after she was born and has had no contact with her since. October of 2018 her grandfather passed away and she was very close with him, I don't think she has processed this.The past year it seems to have gotten worse with her. It started with her just being extremely disrespectful and getting angry about everything. She uses discord to meet and talk to friends, one day she left it logged in and we were able to see what she was doing. Unfortunately she was fabricating stories with people she talked to, making her life out to be awful and tragic, when in reality it's not. She doesn't have a perfect life, but we do what we can to give her a much better life than we had.She also was having online relationships with multiple guys at the same time, even while she had a boyfriend from school. She lied about all of this as well.We had to take her iPad, computer and phone away from her because this was the only way we could keep her off of discord. If she had any of her devices, she found a way to connect to the internet.I don't mind her having friends and using discord, but every time she uses discord she gets wrapped up in these stories and drama, then she turns into a brat, starts self harming, even at one point she ran away.I had a talk with her recently and came to the conclusion that I don't want to keep her from her friends. I was the same way when I was her age, I had trouble making friends in real life, and the internet is where I socialized. I agreed she could use discord on her computer but I would be monitoring her.Not even a couple days into this she's turning right back to how she was before, I also read some of her conversations and she is again lying about her life, and she is currently telling 3 boys she loves them and that they are in relationships.I honestly don't know what to do at this point. Someone please give me some advice.EDIT: I forgot to add that we have had her in therapy for 6-7 months. via /r/Parenting https://ift.tt/33GxtGl