As the Story Turns...

So I have to be vague as to not give away spoilers...

But my second novel is ever-changing!

I began it with the idea that character A and B meet. The story follows the lives of A and B. Simple, right?

But then in introducing character B, I end up introducing character C who was to be a character who was casually mentioned in a paragraph and...now character C's story is taking off.

And sure, character A and B are the main characters but character A is being left in the shadows by the story of character B.

I'd love to write an outline and stick to it, but I've never been able to work with an outline. I let the story progress as it goes. Might this be the wrong way to write? I'm sure it is, but I also think if you write and pray about it and write and pray some more, things can change - and for a reason. Now if only I could discern the reason!