It's too early to tell, but perhaps she could end up laying the groundwork for the Brotherhood? Or at least go over to Erik's side if he decides to split from the X-men? I think it might be better in that regard for Erik to follow her rather than Charles. But that's just my two cents.

Also, like Wolverine has been seeing parallels between him and Atticus, perhaps something about Estella could remind Erik of himself at a younger age. The more I think about it, the more parallels I find.