She was born on November 6, 1989 in Quezon City, Philippines. She is the youngest sister of a very popular Filipina actress Vina Morales. Shaina began her acting career at the age of seven, when she was cast in the Philippine drama series Lyra, playing the lead character. She was discovered by ABS-CBN and became part of the Star Magic Family at a young age. Magdayao was included in the cast of the just-revamped Ang TV show, Kaybol. She was then brought together, with two other child actresses of the 1990s, Camille Prats and Serena Dalrymple to star in ABS-CBN's afternoon drama series Marinella, playing the role of Rina.
