I find her extremely brave

Both are quite brave, but went with Belle because she puts herself in danger numerous times to protect others, despite being clearly uncomfortable in these situations. Nala's brave too, but it's suggested that she is quite physically strong anyway, so it's probably not as big a deal for her.

But yeah. Both have some pretty awesome moments!

How is Nala brave?

^striking out into the unknown to try to help your suffering people isn't brave?

I think Belle was gutsy to go into the west wing but it was far more foolish than anything.