The reason a lot of people in Australia dislike Brumbies is because they're considered "ferals" and "pests" because they break down farmer's fences to eat the crops.
Most people think the best option is to shoot them all! Thankfully there are some smaller groups who capture them, gentle them and find loving homes for them.
OP, I'm insanely jealous of your opportunity and I think Brumbies are lovely. They're usually very hardy, sturdy, solid little horses that are very versatile. Just ignore your "friend" and you'll be able to prove her wrong! ;)
Satin Reign aka "Misty"... my life, my love, my everything.