Unremembered (2013) by Jessica Brody? The girl is named Seraphina, not Sarah, though the names are close. A couple reviews mention her as "Sera", hence the recollection, I guess.
When Freedom Airlines flight 121 went down over the Pacific Ocean, no one ever expected to find survivors. Which is why the 16-year-old girl discovered floating among the wreckage - alive - is making headlines across the globe. Even more strange is that her body is miraculously unharmed and she has no memories of boarding the plane. She has no memories of her life before the crash. She has no memories period. No one knows how she survived. No one knows why she wasn't on the passenger manifest. And no one can explain why her DNA and fingerprints can't be found in a single database in the world.
Crippled by a world she doesn't know, plagued by abilities she doesn't understand, and haunted by a looming threat she can't remember, Seraphina struggles to piece together her forgotten past and discover who she really is. But with every clue only comes more questions. And she's running out of time to answer them. Her only hope is a strangely alluring boy who claims to know her from before the crash. Who claims they were in love. But can she really trust him?
Found with the Google query
sci fi book "purple eyes" sarah plane crash android.