I took it to mean that Adrienne realizes that her life might be short and you should be with someone who wants her. Perhaps seeing Justin with Eve made her decide that Justin isn’t into her anymore, along with the fact that Lucas is still interested in her.
i also think she is following her gut that the feeling just isn’t there anymore!! Can’t say I blame her. However, if she gets bad news you can bet that Justin will want to be there for her.