I think moms work hard. Every mom deserves a vacation. I would recommend CA if she hadn't traveled with the baby before and prefers a short trip. It would be easier. However, Hawaii is a good option, too depending which island she will go to. The main island is good for family travel. Hotels are close to the beach and shops are nearby, too. Everything is very convenient. If she is in CA, the flight will take about 6 hours one way.
I had a post for the mom who planned to take her baby for a short trip a couple days ago about some experience I had traveling with a baby. Hope that would help.
Have a good trip.