(Original post by intermediary)
I'm not sure what made you think she wanted you to look through her messages (she might have, I don't know), but I don't think it's something you should do in future. Messages are personal and I'd be really upset if someone went through mine. But regardless, it's done now so no point in going over that anymore
You're clearly a very compassionate, kind and caring person and I know not being able to do anything makes you feel helpless. Unfortunately, you can't make either friend stop. Stress tends to make bulimia worse so any attempts to push someone into recovery will generally be counterproductive. Just being there for them and offering a safe space in which they can talk without receiving judgment is more than enough and a great service to both of them. You might want to send them a text just saying that you're always there if they need a chat.
If they open up about bulimia and choose to talk about it, you might want to share these tips as, although purging is always bad, it's not going to stop people doing it so it's best to be as safe as possible. Check if they're drinking Powerade or coconut milk after purging as this restores electrolyte balance in the body (electrolyte imbalances are caused by purging and they can be very serious- it's why bulimia is linked to death). Also, if they purge anything which looks like ground black coffee (but isn't food), they need to get to a hospital right away as it's likely to be internal bleeding. If they purge bright red blood, it's generally not serious and is usually attributed to scratching the back of the throat. Using an 'instrument' (toothbrush etc) is more dangerous than hands as many people have choked on it. Never brush teeth after purging as this just rubs the stomach acid into the enamel- just mouthwash, then brush teeth much later.
There's also a bracelet system that's helped quite a few people. The way it works is a person puts on, say, 1+ bracelets and they have to aim to have all bracelets off by the end of the day. Each bracelet equals one piece of food, or meal (whatever the person is comfortable with), that isn't purged. So, say she chooses to start with two bracelets, she needs to keep down two pieces of food without purging to end the day without the bracelets. She might have two bracelets for a week, then move on to three, and so on. The way this works is it helps a person to overcome the eating disorder voice. Bulimics generally find it difficult to reason with themselves when they want to purge and this bracelet system offers control, the same as purging. It makes not purging more justifiable as they know they need to have the two bracelets off at the end of the night to complete the 'task'. This can also work in reverse, with each bracelet equaling a purging session. So, if they usually purge 4 times a day, they should put on 3 bracelets and remove one each time they purge. Once they've removed the 3 in a day, they can't purge again until the next day. The number of bracelets slowly decreases until they're not purging at all (hopefully).
You might also want to ask if they think it'd be beneficial to see someone, like a counsellor, to talk about their issues around food. Apart from that, and the couple of things listed above, you can't do anything that will 'fix' them. All you can do is offer support which is a huge help to anyone with an eating disorder. Remember to take time for yourself though, as I said in the first post. You sound very stressed. As much as I'm sure you love your best friend and care about the other friend, YOU need to come first.
Aw thank you, that's very kind