<human>: Hi, my friend "Alex" has always been on the thinner side. But over the last winter she's lost a lot of weight. I think she went from ~110lb to just above 80lb. She's 5'5". At first I didn't notice Alex losing weight, but after she came back from her vacation, the difference was remarkable. 

At first I thought it was temporary, after all, she looked gaunt and sickly. Surely it was because she caught something, maybe the flu, which she said she did catch. However, she hasn't gained back any of the weight, and soon after winter, she stopped having her period entirely. That's when I started being much more worried. I've asked her to eat with our family, with my sister and I at restaurants, which she's accepted, but only eats a tiny amount. 

I've shown Alex info from the web about how extreme weight loss can lead to loss of period, and she went to talk to her doctor because of it, who agreed that her weight was the issue, but she still hasn't gained any.

At this point I'm pretty sure there's a deeper issue. She's probably not bulimic, based on her eating habits, I'm pretty sure she just doesn't eat food, much less have any food to throw up. 

Is there something I can do to help my friend? Would talking to Alex's parents be too far?

Could you distill the essence of the text into 1-3 sentences?
<bot>: My friend's dangerously underweight. So thin that she's lost her period, and I'm don't know how I can help her.