Cora Question

I'm in a rewatch and on S2 (first time poster on here, so please let me know if I need to add spoiler tags in the post, ty!)

So, is was established in S1 that Regina had control over who she brought to Storybrooke with the curse. What confuses me is why she was so worried that Cora would come with her in the curse... couldn't she have just ..not brought her? Especially since she wasn't even in the enchanted forest anyway? If I am missing something, can someone help me out? Thanks!