Believe it or not, I remember that. The point that Abby was trying to make, and correctly so, that it IS possible to get pregnant without penetration. She was warning girls not to pet without their clothes on. Enough rubbing the right way and that sperm can get in and do its deed. It DOES happen, but it's rare.
Abby would have been better off to point out that one thing often leads to another. If a girl doesn't want to be in the position where a naked guy is trying to convince a naked her to open her legs because she's come too far to say no now she should stop far short. The warning should not have been about sperm accidentally finding its way into her vagina without penetration. It should have been about dancing on the edge of a pit you don't want to fall into.
Shalom.