well, her one line was originally going to be two consecutive lines. I think it really would've been better if they had left that other line. it was something to the effect of "Hmmmm, what do you think Sarabi? I'm not so sure if they're hyenas spotted in the Pride Lands" I forgot where I was told that, it might've been a script that had all the left-out parts.
also perhaps some lines during Scar's take over with her comforting Sarabi and Nala would be nice.
and personally I'd enjoy seeing a little dialogue between her and Sarabi after the cubs have left about their own younger days (I suspect Sarabi of being as mischeivous as Simba XD). I mean, we don't even know for sure if she was even the same age as Sarabi or if they've been friends a long time.
another location could be after the father-son chat, they could've shown Nala's return and the reactions of Sarafina (as well as probably some other pride lionesses). that would be some key personality development as we'd see how exactly she handled the situation.
I just don't have any idea myself on what exactly she should say lol