It's entirely doable, but it does get a little ugly in some spots, like Hwy 1 just before Santa Monica. (Unless someone can chime in here with an alternate route.) But you can always plan your trip so that you can pass that section early on a Sunday morning.
Hwy 1 cuts straight across the Palos Verdes Peninsula to Long Beach, but if you can stand the climbing, Palos Verdes Drive along the coast is a memorable (in a good way) ride.
But once you get to Seal Beach, it's going to be nothing but bliss. I've never done the whole trip in one sitting, but I've ridden every stretch at one point or another.
How many days are you taking?
Camping or hotelling?
Have you and your gf (kudos btw on finding an adventurous rider girl) finished a century or done any ride this long before? (Sometimes the things that sound like fun in cocktail party conversations don't end up quite like we expect.)