Well actually since it'll be during the end of Scar's reign Sarafina wouldnt be "that" old, of course she would already of had Nala and maybe Mheetu . Although when the story progresses then she will become a grandma and so forth. But since its not up to me i dont know, you can if you want to, just she may be a bit older than the other lionesses except for Sarabi and maybe a few others.