The other reason Molly had to disappear

As I've said before, Lynn's need to avoid certain parts of her past translates into the strip. The greatest example is when Annie and her family had to vanish so that Lynn couldn't honestly re-examine the collapse of her first marriage and confront the terrible possibility that maybe, she wasn't totally the victim like she likes to think. The second great example is how Molly lasted just long enough to make sure that Connie didn't learn enough to tell Elly that she was making a mistake with April. It seems to me that Lynn isn't facing up to the fact that her strip made her children's teenaged years a big freaking mess and doesn't especially want to remind herself of that. To that end, her stupid need to keep the cast small marched in lockstep with her need to not see herself as being a jerk to her family; thus it is that Connie looks back on a conflict that never really got resolved until years later and tells Elly to stay the course with the Martian.