Follow up responses can be very successful, but it months have passed by between emails, I would just start over from scratch. Attractive women receive 15-20 emails per day minimum, and won't remember one email from a month ago anyways.
Just make sure that you use a subject line that is bound to get her attention. I like anything that suggests doubt, and qualifies the recipient; or something funny and off-the-wall.
If you sent a girl an email with no response, 4-5 days later, you can follow up with a canned email. I won't provide you with the exact wording as it depends largely on your personality, overall message in your profile and what you're looking for, but you can find the rubrics you should hit on in my post here:
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The important thing is that you make it so that its not a big deal. Don't try to make her feel guilty about not emailing you back. Make her understand that you get why she wouldn't email you back. Be fun and playful.
The odds of getting a response are lower on the second email than by emailing the general public, but I've found that canned emails are just as effective as personalized ones, so its worthwhile for economy's sake.