My Story is Sprouting a Twin

So I'm working on this story and I get somewhere around the fourth or fifth chapter when it starts to sprout off into a different direction than I thought it was...but at the same time I am still writing the original story. So here I have one story, trying to be two.

Now, I'm no stranger to letting the writer take me where it will. I don't write my stories, the stories write themselves through me. But this situation is completely new to me. I've never had a story do this. I hope I'm describing this properly so that whoever reads this will realize what it is I'm saying. I have the original story, I'm still writing it, I'm still letting it take me where it will. On the other hand though, I have a new story, same characters but different things happening. I think I can pinpoint this down and see where it happened. As a consequence of my MC's actions in one part of the book, the story changed. It was like, what happens if when she does this, this happens instead of that? Where will she go? What will her and the rest of them do now that something has changed?

I don't know yet...which again is nothing new to me.

So here's what I would really appreciate from you; your thoughts, your advice, your opinions, whatever comes to you about this. Be nice but not necessarily gentle. If you think it's dumb of me to allow this to happen, then say it, just please don't be a smarmy git about it..... jk jk guys, I luv ya and I know you'll give me the best advice you can. Again, I really appreciate it.

I think that this is completely fantastic. Let it continue and develop. Let the story grow. By stopping one or the other you can change more then the outcome of the story. Think of it like life. When we are faced with a problem, we know that there are diff erent outcomes/endings. Usually the ending is the most important part, you want one of the choices that end with success. Does that mean there is only one right path? Hell no. There can be multiple roads to the final sentence. Some may just be longer, curvier, harder or any variation. It's like the books where you make choices as you read, not all endings are the same but they're not all wrong either. Just because you go right first today and find a good ending doesn't mean you can't turn left tomorrow and find the same or better ending. Point is...there is no harm in it. It can even help you. But if it does become a problem, you'll be the first to know.