Replying No to an RSVP is handled via Splash Forms.

To allow guests to RSVP no:

1. In your Event dashboard select the Registration Form touchpoint.

2. In the Form Editor click the Add Question button on the bottom-right. 

3. In the pop-up, locate the "Are You Attending?" question under the Template Questions tab.

4. Select the question and then click the Add to Form button at the bottom. 

5. Save your changes.

Now, when your guests submit their RSVPs on the event page they will be able to select whether or not they will be attending.