Canon Background
https://awoiaf.westeros.org/index.php/Obara_Sand

In-Campaign
Prince Oberyn was lounging in brothel barge in Planky Town at the dawn of 287 AC, with his arm draped over Othello, when a gristled old knight barged in. The man, Ser Darron, sought to hire Othello as a shipwright. Oberyn objected impatiently, explaining he and his daughter had already agreed to a contract for passage to Vaith aboard Othello’s boat. Before Oberyn lost his patience Obara lost hers and entered the cabin complaining of boredom. She challenged the knight to a series of contests and if bested in the majority would convince her father to release Othello from his contract. This was agreeable to all.

The following Day Ser Darron narrowly bested her in the horse race. They traded the lead position several times acorss the sands, pier, and barges that made up the course… but Obara fell short of her leap from her horse’s back to the deck of the final barge. In the whipping contest her hand was deft and more skilled than that of Gregoriy. In 2/3 rounds she was able to cut the blade of grass clenched between her father’s teeth while Gregoriy only achieved the same feat with Ezzelina once. In the sparring Darron proved his sword to be more skilled than her spear, bringing the competition to a close.