Consider the following:

> 
> Not only does she keep cats but she also keeps dogs.
> 
> 
> 

I wonder why "does" is before the subject. Is it a rule, governing parallelism? And also, is the regular form acceptable too? I mean:

> 
> Not only she does this but she also does that.
> 
> 
> 

Also, is there any other rule governing parallelism?