I love Sarafina! The poor lioness only had a single line in TLK, although she was originally going to have several more.
---Personal theory about Nalas father---
I believe that Scar and Sarafina have been friends since cubhood. I think Sarafina was a true and loyal friend to cub Taka, someone to confide in and get strength from. I think they became a couple as they grew older, but Scar drifted out of Sarafinas reach as he became more obsessed with revenge and power. So changed from the cub she once knew, Sarafina decided to break it off with Taka/Scar, but she was already pregnant with Nala at this point. Yes, I believe that Scar is the father of Nala, and have done so for years.
I know there is no proof in Nalas appearance to say who fathered her, Nala is a spitting image of her beautiful mother.