you need to add a:

.cform fieldset { width:auto!important; }

to make up for the destructive WP theme CSS.

via:

.cform select { … }

you can adjust font size, width etc.

If you do make it wider, you might want to make the form wider as well:

.cform { … }

I thought I was pretty specific. :-)

1. goto styling->CSS editor
2. scroll to the bottom and add
   .cform fieldset { width:auto!important; }
   .cform select { font-family:arial; font-size:11px; width:315px; }
   .cform input.sendbutton {  width:315px;  margin:5px 0 20px 80px; }
   .cform label { font-size:12px; width:70px;}
   .cform label span { width:70px;}
   

That's about as much space as you can make with the given theme (image limitations).

If that's not enought you have two options:

• pick a different theme
• have the field label move to the top and thus add 50px to the field width