Yep. Lack of realistic prospect of cooperation working and the asymmetry are key here. I don't think any option either or both of them can take will save Sam, but Sam could possibly save Caroline from the most serious charges by taking full responsibility for the decision to transfer FTX customer funds to Alameda (except I suspect there are other issues with Alameda's compliance they could still nail her for)

Caroline's option to save Caroline regardless of what Sam does by testifying looks a lot better.