it is highly prevalent among birth announcements in Australia in the last few years.
My half-niece is named
Sienna Jayde.
My friend has a niece named
Sienna.
My friend has a baby named
Izabella Siana-Rose (pronounced the same even though it makes no sense..)
I'm pretty sure its top 10 along with
Emily,
Sophie,
Chloe,
Charlotte,
Lily etc.