RSVP cards are often post-cards w/ addresses and postage already included on the flip-side of the card. It’s fairly tacky if it’s not pre-addressed/stamped.
Bob-Just flipped it over. Yup, preadressed/stamped.
If sitcoms have taught me anything, its that you must pursue this girl etv78! Pursue her like a wolf pursuing a lamb! It may take years of emails, flowers sent to her work, singing love songs outside her window, but eventually she’ll come around. You may need to build some kind of chamber that turns you into the “cool” version of you, but if that’s what it takes, do it. A wedding is perfect, its a big event and you can use it to declare your love publicly. I suggest passing a note to the DJ when the dancing starts to play your music and do a specific dance named after you that you invented. Bonus points if you can get others to background dance for you.
So how did the wedding go, in the end?
Was coming back to answer that very question! 
Was not AS soul-crushing as I feared. Yeah, it bummed me out to be alone, but I had fun nonetheless.