7. There Is No Such Thing As Being Too Close
You do everything together because you love each other and hate everyone else. You know every single piece of clothing in her wardrobe and what looks best on her, so when she rings up freaking out six hours before her date, you talk her through her options. You then talk about everything else that you've done that day - literally everything. Because you know she's come to you looking for some reassurance and familiarity and it's your responsibility to give her what she needs. Which obviously includes all kinds of bodily functions and the kind of honest dating advice that might sound mean coming from someone else.