Since Shrek's Swamp was vacant, Lord Farquaad probably proceeded to send all of the fairy-tale creatures there. Then, since Shrek didn't interrupt the tournament, Farquaad probably picked a knight to rescue Fiona, and he could've gotten killed or something, like all the other knights. But, if you'd like a tiwst, maybe that knight could be Prince Charming, and since it was planned that he would rescue Fiona, Dragon probably would've let him through, and he would've rescued her. But of course he isn't her true love, so the kiss wouldn't work. Then Fairy Godmother would've used some love potion or something, and made her kiss him. Then her plan would've worked, and poor Fiona would've been married to her un-true love. Shrek is definitely an important part of Fiona's life.