One of the main characters. Bio is quoted from https://www.mane6.com/characters/arizona/

Prairie born ‘n raised, Arizona is the youngest daughter of Texas and Minnesota, Head Bull and Cow of her cattlekind clan.

Despite her small size, she’s incredibly strong. Though lacking in experience, she’s undeterred by obstacles. Many older folks underestimate Arizona, but few are more dependable or trustworthy. When called to action, her powerful headbucks and quaking stomps send opponents flying, then she reels ’em back in with her trusty lasso.

Arizona was the only one among cattlekind with courage enough to answer the Council’s call in search of Foenum’s Champion, knowing full well what dangers she faced. Thrust into the wider outside world, Arizona tries to make sense of it all (or decides not to care) while she charges headfirst into the fray.

Quoted from the fan wiki:

Arizona, even being such a young cow as herself, has a big heart: she loves her homeland, and believes that everyone else in Foenum also deserves a free life. She's courageous, ready to help anyone in need and stand her ground to save the whole world. Although Arizona's enthusiasm and being too honest can lead her into trouble. She's not a cow of words but rather action: without thinking, she's ready to dive head-full into the events. Arizona also tends to show more of her cocky side, throwing some snarky comments toward her opponents. 

Being the primary role in a mostly unpaid fandub project, Arizona's VA will be paid a flat rate of $150. Do your best to sound just like Tara Strong! Here's a video to help: https://www.youtube.com/watch?v=JNhVe-PR7zQ