Get her out of the college -- she needs a change of environment, since apparently the problem started there.
DO NOT let her run your family's life, forcing everything to revolve around her refusal to eat normally, her deteriorating medical condition, etc. Aside from being harmful to the whole family, it won't do any good, and will probably exacerbate her psychological condition. Gymnast Christy Henrich died after several years of anorexia -- just a couple of weeks before her death, she won a "negotiation" with her mother, who agreed to take her to a gym so she could work out, after Christy said she thought she "might be able to eat something" if she worked out first. It says something about the relationship that the family had allowed to develop, that with Christy very close to death, they were still letting her control them with insane demands.
You've got a tougher road than if your daughter was under 18, since it will be legally difficult to force her into any treatment or living location that she doesn't agree to, except for very brief periods when a court finds that her life is in imminent danger -- a couple of days in the hospital and a couple of pounds gained, and she'll be out of danger (for the moment) and free to leave and start refusing to eat again. Hopefully, you have financial control over her, and can use that effectively. Don't give any rewards for eating, give rewards only for actually gaining weight (anorexics will often go to great lengths to avoid weight gain, vomiting in secret after eating a little in front of people who are demanding it, etc.). More to the point, withhold anything she wants that you can possibly control, until she meets weight gain benchmarks.
Consult with a physician who is experienced with anorexia, and find out what weekly weight gain amount is safe and realistically possible. Then make it clear to your daughter that she is getting NOTHING she wants from you if she doesn't keep to the weight gain schedule. Make it clear that if she behaves like an irresponsible child, refusing to attend to basic health/life functions, you will regard her as an irresponsible child.
And don't let her go back to school until she has regained ALL the weight she needs to, and a doctor certifies that there is no benefit to any further gain. I've been paying attention to this disorder and the various approaches to handling it for many years (I was involved in ballet and gymnastics, and also went to the sort of highly competitive prep school where this disorder was all too common), and one of the most common mistakes I've seen is the pattern of anorexics being allowed to return to "life as usual" as soon as they gain enough to be out of imminent danger of death. But at that weight level, the body chemistry is still severely whacked out, and the brain continues to function as if it's in starvation mode, failing to produce the hormones that drive normal hunger, and thus convincing the anorexic that she really doesn't need to eat more.
Anorexics are usually very goal-oriented. One of their goals is thinness and absolute control over their eating. However, most are driven to achieve in other areas as well -- some in a sport or modeling, or something like that, others in academics. Try to structure things so that any financial or logistical support for any of your daughter's non-anorexia goals is strictly and explicitly tied to gaining weight. The goal-orientedness needs to be redirected, with the person forced to view weight gain as essential part of reaching the goal(s).
Steer clear of tocuhy-feely type therapists. They seem to be the most common style in "treating" anorexia, but it's hard not to notice that most anorexics don't get well for many years, and some of course die. While it's true that the anorexic needs to develop a sense of control over her life, to replace the role dieting/overexercising is playing in her life, there's a big place for the "tough love" approach. Let her control whatever she wants to about her life, if and only if she's gaining weight. Let weight gain become the ticket to control.
MOSTLY AGREE WITH YOU.
Certainly BEHAVIOR MOD is CRUCIAL, imho.
Not all touchy feely therapists would be hurtful in this situation. If she is touch starved--highly possible--it can be a very crucial aspect of behavior mod. I'd reward her with touch to strengthen the message that she was loved period--every chance I got and especially as reinforcement.
Certainly the family needs to be cooperating, imho, with a family systems approach type therapist to dealing with this problem as well as the very crucial behavior mod.
You clearly have strong opinions, borne of experience and observation. I appreciate them. Your "tough love" approach, however, runs counter to the advice we've gotten from the handful of professionals we've already discussed this with (and this is all in the last 48 hours!). But I do admit that their approach might lean too hard toward the "touchy-feely," and I will heed your caution. This is not a note of disagreement, at all. It's a note of thanks. Your input goes "into the hopper," with all the rest of the valuable FR advice I've gotten. Merry Christmas.