This side quest can be completed after you visit Jahara – Land of the Garif and speak to the Elder. Return to Rabanastre and look for a tall Viera in Southgate standing near the Chocobo Stables on the east side of the zone.
Speak to her and she will explain how she yearns to find a soul mate. She will then walk off towards the center of Rabanastre after your conversation with her.
Make your way to the Southern Plaza and search for a “Lovestruck Man” standing on the north side of the fountain in the center of the plaza. The man will tell you about a beautiful Viera that he saw come through the area.
Travel to the Yamoora’s Gambits shop and search for the Viera one more time. She can be found on the upper level. Speak to her again and she will mention that she is going to go get a drink to “wash away the fatigue of [her] journey”.
Find her one more time on the top level of the Sandsea and speak to her again.
You now have the option of setting the Viera up with the Lovestruck Man that you met at the fountain or with a man named Lord Vain in Yamoora’s Gambit Shop.
Selecting Lord Vain will end up with you receiving a 
Loxley Bow as a reward but choosing the Lovestruck Man will net you a Loxley Bow and two 
Hi-Potions.
Return to fountain, speak to the Lovestruck Man and then return to the Sandsea and speak with the Viera again.
Go back out to the fountain one more time and speak to the Viera to obtain your reward.
This concludes the Viera Matchmaking side quest.
