As a teenager, Foster was on a school bus that was bombed by the IRA, the vehicle targeted because its driver was a soldier in the Ulster Defence Regiment (UDR). A girl sitting near her was seriously injured. She was a pupil at Enniskillen Collegiate Grammar School in Enniskillen, County Fermanagh, from 1982 to 1989, and attended The Queen's University of Belfast (QUB), where she graduated with an LL.B. degree. Her political career began at Queen's University after she joined the Queen's Unionist Association, part of the Ulster Unionist Party (UUP).