Tween Daughter – Help Please

My daughter is 11 and went through puberty at 10. My son (her twin) is 11 and has not yet gone through puberty.

I’m having a hard time connecting with her and she’s keeping stuff from me. She goes right to her room when she’s home and onto her iPad to chat with friends. I learned from another mom friend that she’s dating someone yet when I asked her, she outright told me no.

I’m having a hard time with a few things:
-the moms and I talk to keep tabs on the girls and look out for each other (my daughter says that she doesn’t like that we talk about them)
-her tone has become so rude and snappy
-she is critical of the way everybody acts other than her friends and sometimes even her friends (ex. So and so is annoying and says this about everybody)

We have taken away the iPad at times but she just gets angry and says that we don’t understand, which is probably true but she is no longer interested in academics and “needs” to talk with her friends all the time and was “dating” someone and lied about it.

I’m worried that she’s going to stop talking to me and do stupid things like I did when I was a kid. I want her to trust me and let me be there for her, but I don’t know how to do that when she is acting like this.

What do I do?