Further to my last post in reply to Clairee, I've been doing a bit of reading and it turns out there's such a condition as vomiting as a form of self-harm. It's possible that's what Linda's been doing and explains the absence of the compulsive food behaviours found in eating disorders. Linda vomited after Mick undermined her about Babe being thrown out. It was also implied she did it during the sit-in at Ian's restaurant. Self-harming is compulsive behaviour that relieves stress, so this fits the pattern.
Thanks for the nudge, Clairee! I think self-harm fits what's so far been shown of Linda's behaviour better than bulimia.