I've had this problem too, so I know how you feel. I think most of the advice I give you will be unpopular opinion on this board, but I will go ahead anyway.
I've been a vegetarian for my whole life, however went vegan when my eating disorder intensified. With eating disorders, it's very hard to determine motive regarding going vegan/vegetarian. It is very common for people with eating disorders to adopt one of these lifestyles as a method of restricting. One of the most important aspects of recovery from an eating disorder is to EAT. It's hard to make rational decision/work through any underlying issues with a malnourished brain. If you do want to attempt recovery vegan, it's super important you get all of the nutrients you need, including plenty of fats and protein. Your brain needs fats to repair itself!
The restrictive nature of a vegan diet can also take it's toll on obsessive thinking, so I have found that being flexible is handy. I don't eat eggs or dairy on their own (don't really care for them anyway), but I will eat just say a biscuit or piece of cake with dairy and eggs in it if that's all that's available just to challenge myself. The restrictive nature of a vegan diet is very similar to that of an eating disorder (restricting oneself socially, etc) so I've found this flexibility to be a huge help in my recovery.
Parents and therapists can also be very opposed to a vegan diet in an eating disordered person. Try explaining to them why you want to be a vegan. I've also heard of people compromising by eating vegetarian until they're recovered, and then going vegan. That might work for you?
I've chosen to eat a (mostly) vegan diet because of personal morals, not because of my eating disorder. I'm sure your motive is one of compassion also, and that is great! Please just remember to be mindful of your own needs. Your health/mental health must come first! feel free to message me if you need to talk.