Sinclair said it was an anxious wait holding out for a phone call from selectors on Wednesday night.
"I got a phone call at 9pm [on Wednesday]. We were told to expect a call that evening so I had my phone on me all afternoon," she said.
"I was even doing training with my phone in hand so it was good to finally get the call in the end."
This will be Sinclair's last year in the squad as she finishes her studies at John Paul College this year.
Depending on what university she goes to, she hoped to play for an ANZ Championship side in the future, Sinclair said.
New Zealand Secondary Schools coach Marianne Delaney said she was pleased with the team following a tough selection process, which included 29 players.