Now if she still is willing to pay full price with the one camera, then I would just make sure you take LOTS of b-roll before and after when you get a chance so that you can spice up this one cam shoot because it will need a lot of spice! 😉
Me and my colleagues have found certain ways to add spice: We put in extra video of messages and best wishes from friends and relatives (and from celebs occasionally), unbeknowst to the bride and groom. We insert stills of important milestones in the couples lives: childhood (never fails to draw amused smiles), graduations, overseas trips, etc. We add footage of the couple reiterating (before the wedding day) how the other attracted him or her (but this is now common practice everywhere). All of these are value added, which will be greatly appreciated by the client.