Welcome to the wonderful world of parenting ;)
I know from having a 19yo daughter you go through the boyfriend issues and all sorts of things but the nicest part is that she will come to me before her mom. She and I have a really special relationship and she knows daddy will give her great advice and I will always be in her corner. It sounds like your daughter is definitely preoccupied with her emotions and her world seems like its crumbling around her. Just be supportive and she will pull through with flying colors.
Billy