Daughter stopped eating?

i have two daughters,14 and 12.The 14 year old has NEVER been family oriented.Never really talked to me or anything.She hates family but adores her friends.The 12 year old loves family on the other hand.I tried everything to get her to like me and be family oriented.I took her to therapy,took her out and everything.So i just gave up.She is a good girl.Good grades respectful and all that.Well in the car we got into a fight and she said how i only care about her sister and noone cares abut her and she cant wait till she turns 18 so she can leave us all.We were on her way to mcdonalds but then she said you know what i dont want anything." She didnt get anything after i told her to get.She has not ate anything in 3 days.I tried everything,she lays in her room depressed and doesnt even come out,only to get water.She ignores me and wont eat.I tried everything even talking to her but she only laya quietly in her bed and ignores me.What can i do? Advice from someone who has delt with a depressed teen? And yes i take her out just me and her alone all the time.