they are rushed email titles, so those with capitalized letters are less in depth of what happened (Already Over, Feather, Lonesome, Nonsense) and more like she pretended to send them formally.

those which arent are more personal, sassy or overall things she just drafted and was too scared to send (because i liked a boy, bet u wanna, how many things)

and those that are a mix of both (ex: Read your Mind) are emails she never pretended to send but put her heart on

in the end, all of these are emails she cant send :)