How can I help a friend who is suffering from anorexia?

I am not anorexic and never have been, and although I have also had issues with eating before, it wasn’t the same, so I don’t know how to help.

I understand the most important thing is to be supportive, but knowing my friend, just being supportive won’t be enough to help her.

I also understand that I shouldn’t force her to eat. But if I don’t, then she won’t eat. What can I do about this?

It’s my current understanding that this happened due to issues with her body image (despite already being very skinny). How can I help her feel more comfortable in front of a mirror?

She has a therapist, but she doesn’t really talk to her. She would be uncomfortable mentioning it to the therapist. Should I try and convince her to bring it up, or let it be the way it is?

I feel like I already know what the answers will be (something like “just be there for her, don’t make her do anything she’s not comfortable with”) but she’s my best and only friend of many years and I love her a lot. I really want her to get better, especially knowing personally what it’s like to be severely underweight. I don’t know how underweight she is now but she’s said she lost ten pounds in three days, and she looks very sickly.