Hi Marianne,
Unfortunately, we don't have any plans to make the text in the Facebook Store app customizable.
However, you might be able to solve your problem in a different way. I see that you're using a special variant to make customers pick an option from the drop down. This can be accomplished without a special variant, by editing your theme. There's a guide that describes how to do it here: http://docs.shopify.com/support/your-website/themes/how-to-add-a-pick-an-option-to-drop-downs
If you have any questions about how to edit your theme, you can contact a Shopify Design Guru for help, since you're using a Shopify-built theme. Try emailing designguru@shopify.com for help.
