Shadowgandor...
I have a very close friend who has dealt with both issues simultaneously, and move into the same exact position your friend is in, and know several others who have dealt with anorexia. My conversations with them have led me to this conclusion:
Cutting has more immediate repercussions, but it is a tad easier to stop.
Anorexia takes a little more time to effect something, but it's more permanently damaging and is takes a lot more willpower to stop. Cutting is usually more of a choice, Anorexia can become a mental illness, where one starves him or herself without even realizing it. The people I know of never have breakfast without measuring exact amounts of what they're eating, and they do it by habit, not because they choose too. They're literally afraid of not measuring, even if they want to stop being anorexic.
On the other hand, I've discovered that it's easier for me to help my friends with anorexia, because it's easier to visibly see if they're doing well (watching them eat, etc.)
Just my 2 cents. Like Atom Eve said, quick reaction is best. The less ingrained into a person's behavior, the easier the problem is to solve.
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