probably not, cos even when i was younger, i've always thought that simba looks more like sarabi and there's a really distinct difference between him and mufasa, the only similarity really is the mane.

Of course not. Simba's mane color is red, while Mufasa's mane color is brownish-red and Mufasa's muzzle is thicker than Simba. Simba's eyes are bigger too. ;D

yeah i agree with ligtningred

The last time Sarabi saw Simba he was a cub. When her son returned he was a full grown lion. I could see how she would think that he was Mufasa. Scar also thought that Simba was Mufasa.

yes because she hasn't seen him since he was a cub and she thought he died so she didn't know he grew up so it makes sense she would think that