Inner conflict doesn't grow out of plot. It's the other way round—plot grows out of the main characters' inner conflict. You can have your chase scenes and your kidnappings and your great one-liners and your brilliant wonderful sex, but if they don't speak directly to your main character's inner feelings, there's no point to them.
Conflict grows and changes as your character grows and changes. Although the seeds of the problem should be right there on page 1, by the end of the book, the heroine shouldn't be solving exactly the same problem as she faced on page 1. It should be related to her initial problem, but it should be deeper, more complex, developed by the events of the middle.
A very wise author (called ahem—Kate Walker) told me once, "Don't be afraid to put conflict on the page." Make the conflict the centre of your story. Don't hold back.