Did she tear them out post-murder or around that time? If so, probably an effort to appear to polish her reputation in order to contrast better with Travis' soon to be tarnished one. The deleted info probably wouldn't stand under scrutiny in support of the image she wanted to project of her relationship to Travis (ie passive, devoted, long-suffering, and tolerant of Travis' womanizing). The reality being that she gave as well as she got, and then some, with regard to flirting and sexual boundaries, but that couldn't come out in court.
BTW, with regard to ' behavior toward the opposite sex, rabbit fits, and hole fits, so I'd say your assessment is accurate.
She said she tore them out because....Travis told her to; because one set of pages was about the weekend she spent with Jon Dixon, which Travis read about when he snooped her journal, which is what the fight on the Havusupi trip was really about, not a backpack full of make up; and that she tore some out because they were just too negative and suicidal-ly.
In other words, she tore them out after she slaughtered Travis.
What I went spelunking in search of was the why of those specific pages, based on the dates and what else was going on.
The Jon Dixon story was, unsurprisingly, a flat out lie, and one she could not have told TA at the time, because he would have known that weekend supposedly spent with Dixon was an impossibility.
The purpose of her lie about that set of pages (1 of 3) was to "prove" her lies that TA snooped on her, including her journals, and that he became insanely jealous when he found out she had been with any other man.
One of those 100% inversions of reality.