Sorry to nerd on this, but if her speech skill was 10, she'd essentially have space-tourette's and cause everyone to try to kill her when she opens her mouth. On the other side, that's probably why she can talk to animals.
Heheh. Yeah, it could probably be as bad as that or she'd be drastically uncommunicative. Then again, the latter kind of suits Fluttershy, but I'll just leave it as a little joke regarding how charismatic and quiet she is at the same time. 