Do tu think Nala should have had a say in Kovu being banished.

Yes, o at least we should have be shown her telling Simba off.

@boytoy_84; How was Simba following Mufasa's rules?? Mufasa would had at least listened to Kouv's side of the tale before deciding anything. Simba was all like, "Nope, I don't like tu anymore, you're banished!"

I think she was going to speak to Kiara but then she got interrupted.

No

Not really. since Simba is the leader, he has the right to decide to exile Kovu if he feels Kovu is like another Scar.
Simba follows his father's rules and will do the best as being king.

No unfortunately I think it's the kings job to make those decisions.