I know it hurts, but you have to let it go. It is not fair for you to say that you 'need' your daughter (that's not healthy for either of you). She probably just felt overwhelmed and a bit lost herself, and needed some space. She is 18, and fully capable of making decision for herself... And I am sure once she does some introspection, she will be ready to connect in some way again.

Just hang in there, and try to be patient... maybe try to do something for yourself