I think I might have to join you 
I have been reading this thread since my troubled dd17 went through a phase of reduced appetite just before Christmas last year. She recovered and whilst struggling with disordered eating (vegetarian/food sensory issue etc) ate reasonable amounts and maintained her weight.
At the beginning of July she got covid and one of her main symptoms was reduced appetite, abdo pain and nausea. Unfortunately, the same day, she started a mood disorder medication (Aripiprazole) so we never knew what symptom was related to what.
Anyway, since recovering from covid she has stayed on the meds and upped the dose. She has never regained her appetite and feels sick often.
I have found out she has purged in the past and last week I found bags of rotting uneaten food in her wardrobe and drawers. I haven't physically seen her eat a proper meal since the beginning of august.
The most worrying thing is she has lost 5kg since getting covid (now 53kg) and seems to embrace her problem of low appetite rather than wanting to get better.
The last few days haven been horrible as she's no energy at all and looks so thin.
I can't believe it's happened right under my nose. 
She is going to Reading festival for 4 nights on Thursday which I am absolutely dreading. She has newly diagnosed ADHD and is a bit of a risk taker, particularly with alcohol, and will think nothing of drinking vodka on an empty stomach. I fear alcoholic ketoacidosis. I phoned her best friend earlier who she's going with and she had been wondering whether to call me as she's also v worried about her. Luckily she has promised to talk to her and encourage her to eat. And I did mention the welfare tents...
I don't really know what to do. I would love to know her wfh if anyone can help with that (Lougle?)
Sorry it's so long. I guess the speed with which she has lost weight, right under my nose, and despite having read this thread for 9 months, I'm just gutted.