Blue Line/Green Line is a bit of a drag because you have to transfer and Blue Line has gotten progressively sketchier over the years. I used to do this since I live a couple blocks from the Blue Line in Downtown Long Beach. If you do have her drive you from the OC, you can have her drop you at the Green Line station in Norwalk - then you don't have a transfer. Plus, Blue Line is going to be undergoing major track work in the near future so you'll want to avoid it during that time period. The Norwalk station is freeway close, so an easier drop off.
Alternatively, if you are going to be in the LB area, there's the Flyaway bus, which is much easier to manage:
https://flylax.com/flyaway%20bus#Routes