I'm going to do a process of elimination here:
1. It's not a Mattel doll, so it can't be either a Barbie doll or one of her friends or one of her Disney friends.
2. It's not a Snow White doll because her hair's the wrong color.
3. It's not a Kenner Miss America doll because none of them had a name that started with an S.
4. It's not Kayley from Quest for Camelot, an animated film from 1998 (no S in the name).
There have been umpteem non-Disney (like Quest for Camelot) animated films (both traditional and computer-animated) made in the past 20 years, not to mention plenty of animated TV series. Did any of them have a character or kingdom that started with an S?
These are S girls' names that I know of, but they are traditional names, nothing trendy or movie-cutesy.
Sabrina; Salome; Samantha/Sam; Sandra/Sandy (Cassandra? Alexandra?); Sarah/Sara/Sally/Sadie; Serena; Sharon; Sharlene; Sherry/Sheryl/Shari; Sheila; Siobhan; Simone; Sissy (Cecelia et al?); Sonya; Sophia/Sophie; Stacey/Stacie/Stacy (Anastasia?); Stella; Stephanie; Susan/Sue/Susie/Sukie; Susannah/Suzanne/Suzi; Suzette; Sybil