[¯|_(ツ)_|¯]

I know that one time I was scared that my cousin was cutting because I saw some posts on Tumblr that concerned me, and what I did (mainly because it was nighttime and I wouldn't be able to calm down until I at least asked her) was sent her a message through Facebook. I let her know that I saw these posts on Tumblr that mentioned self harm (I gave her her Tumblr name to confirm it was her) and I was really concerned about them and wanted to make sure she was okay. Maybe you can do something similar, only more regarding your own situation?

I recommend doing it in person, though, if possible, or at the very least over the phone. On a day when she seems to be in a relatively good mood maybe you can say you were looking around on Yahoo Answers and came across a question. You can let her know what the content was and why you think it was her posting it. Then you can let her know why this is really concerning to you, and emphasize the fact that if she IS self harming, she can come to you and you'll try to work through it with her.

But, you know your friend better than I do, so if you know a better way, go for it! Whatever makes you the most comfortable and what you think will make her be the most honest, do.