what happened with tom in ventura? who was he with ? what is notable about this incident ?

From the text:

A week after I left Santa Barbara Tom ran into a wagon on the Ventura road one night and ripped a front wheel off his car. The girl who was with him got into the papers too because her arm was broken—she was one of the chambermaids in the Santa Barbara Hotel.

This incident was notable because just the week before, Nick had visited Tom and Daisy, who he believed were completely happy. Obviously, Tom was fooling around with other women even then.