They are implying that the outcome for the girl hitchhiking around Mexico could have been worse had one of the criminals or other bad actors been the one to pick her up. I believe the purpose of the story here is to warn against survivorship bias. Just because something bad doesn't happen to you when you do something risky, it does not mean that the bad thing does not or cannot happen. Someone hitchhiking solo around Mexico (or anywhere) is taking a risk of being picked up by nefarious persons and having bad things happen, such as sexual assault, kidnapping, torture, or murder. The fact that one girl did it for a month with no issue does not necessarily mean that there is no risk in doing it.

The purpose of the Oakland story is to warn that just because something bad doesn't happen, even for a long time, it does not mean that the bad thing does not happen.

>In this manner, she traveled around Mexico for a month, and she never had a dangerous ride.

>the consequences for her would probably have been much worse

These are the two linked statements — if she had had a dangerous ride, the consequences could have been worse (abduction in a foreign country etc.) than the consequences of a mugging in your own city.