Some will be supplied by the party, if you're in government you'll get some from the civil service and - if you promise to give them enough juicy public sector contracts when you get into power - you can usually get people like KPMG et al to provide a few.
Embarrassing stuff nonetheless, she should've just said she didn't know and that her principles were x, y and z. Even the people voting green know they aren't going to get into power.