[Just so he knows that she'd like for him to repeat over and over and over that he won't leave her. She'd like for him say 'Come along, Rose. Get in the TARDIS' a hundred times. She wants proof that only time, the Doctor and a very particular beach in Norway can provide. She knows that none of those things are practical and some of them aren't even possible at the moment. Instead, she'll take what she can have: him knowing that this isn't okay
If I hug you, I'm goin' to be a mess.
[It's by sheer force of will and focus that she's holding it together at all. She knows crying women aren't really his thing. It might also be a bit of a test, although it's an unconscious test. She doesn't mean to issue it. It's also permission for him to close the distance between them and hug her, if he'd like. That part though, isn't really a test. She'll hug him just as easily if given permission to be a mess and sob all over his jacket.]