Two things that might make your friend feel more comfortable:

1. The Pub Crawl is essentially a guided tour. Lenbert is more than just a driver - he gets off the bus and shows you around if you are not familiar with a stop
2. As Rasta Stan mentioned, you will be with a LOT of other people. If she is really worried about what might happen off the resort, she should feel comfort in knowing that there is safety in numbers. (and I say that with the personal understanding that there is absolutely nothing unsafe about visiting the bars on the West End.)

You might also want to show her this message board. I think that might show her that there are many people who enjoy activities off the resort and that is what attracts them to Negril and keeps them coming back.