My friend is on the chat sites 24/7?

I am in my first year of University. I live in halls and on my corridor I have three girls. All of us are now close mates. We're all worried however because one of my mates spends almost all her time on chat sites.Even when she has uni the following morning she will stay on it until 6 in the morning causing her to miss her lectures. She has already failed this year due to unacceptable attendance. She meets guys and then tends to give them her number and talks to randomers for hours and hours. She never wants to do anything with us and says she can't be bothered to go out on a night out. She wakes up in the afternoon and is straight on. I could understand if she was lonely but she has us three and she has many friends back at home.She always says she only talks to these guys because she's bored but the truth is if she is bored she could easily do something fun with us.When she comes into the kitchen to eat her conversation is always about these random guys she "knows".