This is a problem in general when you are working with select lists. The value that is submitted will not include the label. The best way to work around this would be to set the label of the selected index to the value of a hidden form element. You could then reference this hidden form element in the body of the email to get at the label.
The other way you could do this would be to set the labels and values to the same thing so that the label is submitted and not an id.
If you would like to go the first route I have an example page with a js function that is setting the label for the selected index to the value of a form element. You can use this same function call, just make sure to update it to include the name of the hidden form element you create to hold this value.