Your wife is roughly 66% of your size.

66% of a 17' boat is 11'2"

So obviously a direct proportion is not going to work or at least look dignified.

I think if you reduced it down a foot in length proportionally, it would be a good compromise for her without sacrificing any traits. Because of her lighter weight she will be higher on the water and most likely will be waiting for you to catch up every 15 minutes or so. Don't make the cockpit smaller, just pad it on her hips to make her more secure. Plus... don't paddle it. You may not want to give it back.