Synonymous with "She'll be right", etc.
In this usage, "she" can refer to anything, including people (both male and female), animals, and objects.
Most hilarious when used in a situation that will certainly not "buff out".
May also be shortened to "She'll buff" or just "Buff".
Can be used to substitute "oh shit" when shortened to "buff".
Sam: "Dude I think I broke my arm!"
Tom: "Oh she'll buff out"
Alex: "Shit I just rolled my car"
Locky: "Pfft, she'll buff"
Steve (watching his phone fall from a 10th story balcony): "Buff!"