[Plugin: MailChimp List Subscribe Form] Mailchip plug-in widget bounding box doesn’t extend far enou

I’ve recently installed the MailChimp plug-in on my site (https://www.socialmediacoffeehouse.com), and I’m running into a problem when I include the widget in a sidebar. The form boxes are appearing outside of the widget’s bounding box. This means that I do not have the normal background that I would have in any other widget (e.g., a text widget) behind the forms. This also means that there is incorrect spacing between the MailChimp widget and the next widget on the sidebar (as well as too much spacing between the widget header and forms.)

Here’s a link to an image comparing how my page looks now to how it should look. The center image is identical to the one on the left, just with some highlights of the problem locations that I have identified.

https://www.socialmediacoffeehouse.com/wp-content/uploads/mailchimp_widget_errors.png

I’m using the Arras Theme 1.4.3.1 and the MailChimp plug-in Version 1.1.12. What file do I need to edit to fix the widget, and what change do I need to make?

Thanks!