"I am attending a conference call with an international business partner. She lives in China and I live in North Carolina. She created the event and invited me as an attendee. The event start time on my calendar is at 9AM but I'm not sure if that is 9AM EST or 9AM UTC."

When you are invited to an event, the start and end times displayed will always be in the event time zone and not your time zone. So if you live in the EST time zone and you are invited to an event in the UTC time zone, the event dates and times displayed on the event page will be in the UTC time zone.