I have a theory as to who the mysterious woman in X-23 is: 
 
The Woman is an evil version of Laura from the future.
 
Think about it and in terms of the Thompson quote she told Laura, " "As you were, I was. As I am, you will be."

omg you have me confused 
 
 
but u are right 
 
 
so whos this woman ur talkin bout

I dont think its her literally. I think Laura is gonna be LIKE her.  
 
I think...?

@shadow death:Just think who of all people in marvel universe would want to harm both X-23 and Daken,just two names:
Ms.Sinister was stabbed twice both by Laura and Daken and on the other hand Romulus was betrayed by Daken and Logan and seeing as how he used to work that shadowed lady might be his pawn,if I was Romulus the way to harm those I hate would start from the one that looks vulnerable and exposed.
@Gawdzilla:No Romulus is not dumb,you are not in control of other peoples life for centuries moving the strings from the shadows just to be called dumb.

It could also be another one of the X clones, that survived Laura's original escape. 

I think that if she was a future version of Laura, Laura would have been able to figure it out from her scent. Maybe she is another experiment like Laura, but not actually her.