Last night was the very last time I ever saw my marefriend.
Of course, since I'm finally joining the Wonderbolts and they perform all over Equestria, there's a chance I'll see Rarity again.
But she'll never be marefriend again, not ever.
Not after everything I did to her.
The 'Sex' tag is just for when Dashie talks about the stuff, so no sexual contact actually ensues. Seriously, there's even a couple of paragraphs where Rainbow contemplates why it didn't happen