Beginner girl snowboarder, snowboard isn't up to my chin.. will it work?

As a beginner it will work. The board doesn't have to be perfect. As long as it isn't at your waist it should be fine. If you advance you will need a new board. Have fun boarding :)

Yeah itll be fine, the shorter board the more control. You wont be able to go very very fast and you could wash out but if you're beginning it should be okay as long as you have okay balance.

**** these guys, I've been riding park for like 4 or 5 years. I'm 6'1" 160 pounds and I ride a K2 WWW that's not even up to my shoulder, its 145 cm. You'll want a short board if you're going to be riding mainly park... Easier to flex and more maneuverable. Since you're just learning to snowboard it might be a little bit harder to learn on, since longer board have less shake and are generally more steady, but it's worth it to go for a shorter board for park. Trust me.