Teens grades dropping because of social media?

[Cheyenne]

I am the parent of two teenagers, one boy and one girl. My daughter just turned 17 and we have just had ANOTHER argument over her use of social media. The problem is that she is on it for hours and hours and hours, into the wee hours of the morning. She is an honors student, her GPA last year was a 4.17, due to AP classes, etc. She used to belong to the MUN (Model United Nations) club, went to UCLA to represent her school, was president of other clubs, but now it seems her grades are dropping, and it feels like I cannot make her see the connection between her overuse of social media, and her slipping grades. She had aspirations of becoming a dentist, but honestly, I do not see how she can possibly go on like this. Everytime I talk to her about such and such class that has a low grade, I get some excuse. Tonite I took all of her electronic devices away from her. She used to spend hours and hours doing research and homework, but not anymore. What advice can anyone give me?
Thank you.