If someone swerves into your lane, do you move over and risk hitting another car and being “at fault” or do you let them hit you?

I was a passenger in a car recently in a middle lane on the highway, a car in the left lane erratically switched into the middle lane, the driver of my car swerved to the right to avoid the hit and subsequently hit a driver on the Right lane.

The car that caused the accident sped off and the driver of my car was of course at fault for the accident.

What’s the best way to react in this situation? Just let them hit you if you can’t move elsewhere?