in final fantasy 10

Age: 15
Height:158cm or 5'2 ft.
Eyes/Hair: a swirly green/blond
Tribe: Al Bhed
Overdrive: Mix
Weapon: Claws
Voice: Marika Matsumoto (jp), Tara Strong (en)

Description from Official US site:
Rikku is a young Al Bhed girl. Her personality is upbeat and positive, and she is not afraid to speak her mind. She works hard to restore her outcast people to their former glory. Rikku handles mechanical enemies with ease, and can steal items from enemies, too.

Description from Guidebook:
Rikku is a young Al Bhed girl with an upbeat and positive personality. She dismantles mechanical enemies with ease, and can steal items from enemies as well. When Rikku joins the party near the Moonflow, her technical expertise allows you to start customizing equipment by adding abilities to the open slots on weapons and armor.

meeting Rikku
You first meet Rikku when Tidus arrives in Spira. After aiding him in battle, she punches him unconscious, since everyone thought he was a fiend (I wonder how they came to that conclusion -I mean, you do not get much more un-menacing than that).
Later Tidus wakes up in a salvage ship. He and Rikku must now work together. After excavating some underwater ruins, Sin attacks the ship and Rikku, tossing Tidus offboard.

The second (and final) time is at the Moonflow. Just a while ago Tidus and Wakka were fighting a machina that had kidnapped Yuna.
At a beach nearby, Rikku is found washed ashore. It turns out you were fighting her!
When everyone else approaches, Rikku asks to become one of Yuna's guardians.

in final fantasy 10-2

Age: 17
Height:v158cm or 5'2 ft.
Eyes/hair: a swirly green/blond
Tribe: Al Bhed
Occupation: Sphere Hunter
Dress Sphere: Thief
Voice: Marika Matsumoto/ Tara Strong

Description from official site:
In the two years since she helped Yuna defeat Sin, Rikku has travelled with other Al Bhed around Spira, teaching people all there is to know about machina. During the so-called "search for truth" that overtook Spira after Sin't defeat, a group of Al Bhed joined the ranks of sphere hunters. With their airship, the Celsius, as a base, Rikku and Brother founded the Gullwings, and they have been travelling together ever since. As always, Rikku's endless supply of pep keeps the team on their toes.

meeting rikku
Rikku is with you from the start. An imposter has stolen Yuna's Garment Grid and is holding a concert as Yuna. It's up to Paine and Rikku to save the day.
You even get to play as Rikku for a while! Usually it's Yuna who you're controlling.