Is my friend getting too thin again?

[zap.]

I'm so glad that you care about your friend, most girls don't have the courage to speak up

But I think your friend is struggling with anorexia nervosa. It's a terrifying disorder, so notify someone immediately. I am guessing though that someone already knows, since she had collapsed in school. Just give the best moral support for your friend. Say things like "You know I'm here for you through anything that happens" or even something as simple as "You all right?" Just keep on repeating these things, because the last thing you want to do is isolate yourself from her.

Whatever you do, don't comment on her weight. It's triggering either way, trust me. If you say how great she's looking these days, she'll keep on starving herself. If you say she's looking "healthy" or anything other than skinny, she'll continue.

I hope your friend is able to overcome this obstacle in her life, she seems like a smart girl who's just insecure and lost.