I would skip SM unless you really want to see the pier, I spent about 15 minutes on there total.. it was very uninteresting. My wife and I did the Ferris wheel at sunset and that was just awesome, but other than that head to Venice.
Venice is exactly what you picture California to be in the movies. Surfers, beach bums, volley ball, life guards, skate park, board walk, basketball, body builders, break dancers all in eye sight of each other. If you want to cram as much California as you can into just a few hours, this is the place to do it.
Then I would Uber up to Abbot Kinney (
http://abbotkinneyblvd.com/) to get your significant other a nice gift at one of the really cool boutique shops and make sure to get a bite at Gjelina (
http://www.gjelina.com/). I have done that exact day and it is the perfect amount of adventure and it can be as expensive (go nuts) or as cheap (literally you can spend a day waking around) as you want it to be. You get a good mix of being a tourist and feeling a bit like a local.
I did Southern California for 8 days and those two spots were my favorite part (Santa Barbara a close 2nd, honorable mention to Disneyland where Eeyore flexed at me and felt up my arms).
*Another bonus stop in between Venice Beach and Abbot Kinney is the Venice Beach Canals Walkway (
http://www.tripadvisor.ca/Attraction...alifornia.html).
Edit: Ah a few people beat me to these ones, that is fine though. I agree with it being scuzzy at Venice, but I am a germaphobe neat freak and it wasn't so bad that I felt uncomfortable. I wouldn't go there after dark though, that part of the stop should be earlier.