My friend told me she was depressed, should I be worried? What are some signs that she may be suicidal?

Going off an earlier thread of mine, realizing through your guys helpful answers that I was focusing on the minute instead of the larger problem…I realized that I am worried about my good friend and roommate. She told me a few weeks or so that she is depressed, she didn’t quite say it like that, she told me about a story where she told someone about her depression.

I didn’t really know what to say at the time, especially because of the way it was worded, but now I wonder if I should have…She has shown signs that make me worried about her: going out on mysterious walks at 10 or 11 pm after she has had a couple of drinks, not eating or buying food at home, not unpacking or getting her room together, and drinking more and more. One night she came home crying, and I did talk to her about it, and I think I cheered her up.

Anyway, I don’t really know if these are clynical signs of depression, but I am definitely worried about her. Another friend of mine even asked me if she might be depressed the other day, which worried me even more, because if other people are noticing, than it must be a problem. How can I approach her in an easy-going way to see how she is doing and find out if there is anything I can do to help?