"A note from Mattel about unsolicited idea submissions
14 November 2011 at 20:25

As the world’s largest toy company, we receive thousands of product suggestions every year. Given this volume, it’s likely yours is the same or substantially similar to concepts we’ve already received or developed. While we appreciate hearing from our consumers, we rely on our large staff of designers for product ideas. Therefore, it’s our policy to not review any unsolicited concepts and we cannot retain your submission. We don’t assume any obligation in connection with your unsolicited concept.

If you’d like to learn more about how to get into the toy business, you may wish to contact the Toy Industry Association at link.

Best of luck in your endeavors."
Source: link

"Frequently Asked Questions
May I submit a product idea, concept, or material to Mattel?
While we appreciate any interest that you may have in submitting product ideas and materials to Mattel, we only develop products that are based upon ideas developed by our large staff of in house designers or are submitted by professional product designers and brokers with whom we have long standing relationships. For these and other reasons, if we receive any product idea or material submissions from someone we do not have pre-existing relationships, we will not review them and will return it without retaining any copies of it or sharing it with any Mattel employees who are involved in research, design, marketing, or licensing. So, please don’t submit any product ideas or materials directly to Mattel. If you’re interested in soliciting interest in any product ideas or materials that you may have, you may want to contact a professional designer or broker that specializes in consumer products. For a list of these professionals, you may contact the Toy Industry Association at 212-675-1141 or at
www.Toy-Tia.org."
Source: link

I think the official answers above may be based on toy ideas, though. My suggestions are to try contacting Mattel Playground Productions (link), as they're currently doing the Barbie movies. Alternatively, maybe you could rework it into an original movie script (remove Barbie references) and submit it to another company if they won't accept it.

Here is a list of all the Barbie movie writers, from most recent to least recent. You can try contacting them:
Marsha Griffin, Kacey Arnold, Amy Wolfram, Brian Holefeld, Cydne Clark, Steve Granat, Elise Allen, Alison Taylor, Amy Wolferam, Cliff Ruby, Elana Lesser, Laura McCreary, Diane Duane, Linda Engelsiepen, Hilary Hinkle and Rob Hudnut.

Wow! Thank you very much!

You're very welcome :)