I always got the impression that from moment one, Rinoa adapted Squall as a "project", sort of like Myrna Minkoff does with Ignatius Reilly in the book "A Confederacy of Dunces", if you've read it.

Squall's attitude towards her could probably have worked in the way that she sees an even bigger need to "rescue him from himself". This behaviour can often be seen on women who are mature enough to have motherly instincts, but doesn't have a baby of their own to apply them to.