This is a worthwhile exercise for anyone. I recently went without my phone for about 15 hours. I lent it to my daughter because hers had locked her out. I was surprised at how well I managed without it cause it never leaves my side.
I have just finished reading Jonathan McKee's book, The Teen's Guide to Social Media and Mobile Devices: 21 Tips to Wise Posting in an Insecure World. You can take a sneak peak here. The book is easy to read, up-to-date (published in 2017), full of interesting information and real life stories. Jonathan gave some Bible verses and looked at the topic from a Christian world view, but the principles are relevant for all teens. There are discussion questions at the end of each short chapter so I think it would work well as a small group study too. I highly recommend it!
The internet is a tool for communication,
Jordan Lee has an interesting article on her blog, The Soul Scripts, about Internet Drama. In it, she has two suggestions:
http://fervr.net has a new article about social media by Nicki Gangemi. She points out that we should aim to please Jesus in all that we do (including online). 1 Corinthians 10:31 says, When you eat or drink or do anything else, always to it to honour God. Sometimes we can post "Christian" stuff in a way that doesn't honour God. Nicki has some tips on how to avoid this. You can read the article here.
Short and sweet inspirations for Christian teen girls.