I'm actually in two minds about this, I'm not sure, she could have been at Kiara's hunt, but we didn't see her, but I don't think she died. But, I think she wasn't seen in the movie because the voice actor died.

She might have died..those were other lionesses

I recently heard her voice actor died a year after the movie was out, but I didn't knew about this until a few years back in the late 00s. So I think that already answers the question. They couldn't find someone to take in Sarabi's part.

I actually think she did, the actor died and i am pretty sure they did not decide to let Sarbi in but i am sad though :D!!!!!

I would've thought that if she had actually died, it would have been mentioned in the movie. (or - to show it in a sweet and symbolic way - they could have shown her ghost with Mufasa at the beginning of the movie)

I think she was probably still a member of the pride, in the background. On one hand, it seems odd that despite still being part of the royal family we never see another character acknowledge her. But on the other hand, maybe they just didn't have a good enough reason to specifically give her any special screen time. There were some background lionesses that looked a lot like her, so I guess we'll never know.

Overall, I think it's most likely that she was there all along as part of the pride, but had no reason to be acknowledged by the other characters during the story.

of old age.

I think she passed away, and none of those lionesses are her or Sarafina.

One of those lionesses is Sarabi.