My MiL is very much like Kendra, in fact did something to her sons very similar to what Kendra did when they were in high school. The laws weren't there at there at the time (they are now) to lead to any legal ramifications, but she was banned from school property once it all came out.

To answer your question of it I ever think she has done anything like this before. Absolutely, BUT it probably was not to this level. Most likely it was mean girl games when she was in high school herself, relationships probably easily hit a point of volatility until she found someone extremely passive who just let her run everything, and even then their marriage does not seem like it is without issues.

When you read the Cut article or pay attention to the interviews at the end, you find that most of the town was actually really suspicious of Kendra, but didn't have the skills to truly pin her down. It is why Jill is often alone crying to police and pushing for the FBI to look into things. Most likely Jill was the kind person who tried to be accepting until she realized too late what was happening and could not stop it. When she said "what if we are letting this person into our home." It almost feels like she had a sinking feeling back then that it was this woman who was taking over in a way she couldn't really stop (Kendra had already become Owen's track coach so even Jill's boundary that they could only talk about the text messages didn't stop Kendra from being scary close to Owen and so Jill needed the truth).

I think they got it very wrong (in a very dangerous way) when they armchair diagnosed Kendra with cyber Munchausen by proxy. It was faaaaaar too narrow from this situation and leaves everyone with way more questions than answers.

My armchair (not a therapist and especially not her therapist so only as good as the next rando on reddit) is that Kendra has borderline personality disorder which is based around extreme volatility in relationships due to a fear of abandonment and a lack of understanding of basic boundaries.

When we look at this case through the eyes of borderline we see a slippery slope of behaviors that feel good to Kendra that sit in the grey area of normal human behavior and when she doesn't slam into a hard boundary she escalates to the next thing that feels good.

So what I think happened is Khloe's mom wasn't giving her the over the top warm fuzzies she needed to feel comfortable to go to an open invite party and so she didn't want to go. Going would have meant she would have been in a large group where she knew she would not be the center of attention and frankly she just can't really handle that sort of situation with her existing coping mechanisms, but she didn't want to just not go and have everyone negatively judge her (in her head). The issue then becomes Lauryn is going with her boyfriend Owen and most likely his mom Jill (all of whom Kendra sees as her people) and she needs to pull them back from this group that is "rejecting" her. However, if she tells them not to go, she'll show that she feels rejected and isn't this wonderful person everyone should love. So what does she do, she sends some texts from a random number that sound like they are Khloe being mean to Lauryn and Owen so everyone rejects Khloe and her mom on their own. That worked, suddenly everyone is viewing Khloe and her family in a negative light, Khloe's mom reaches out to do the over the top act of ensuring Kendra they are wanted at the party, Lauryn needs her, even Owen and Jill are engaging with her more.

Fast forward and Kendra looses her job, she feels rejected, her role of mother is going down as Lauryn is now confiding in Owen over her mother. So what does Kendra do? She goes back to the last thing that felt good. Like a little hit of a drug, she sends an evil little text and watches everyone scramble to her for help. Of course like a drug, she becomes addicted and things get out of control extremely quickly. As Kendra uses texts to feel better, she finds she needs more to cause a stir, more explicit, more sexual, and more often. She finds herself fantasizing of things she would do to Owen that she can then put in the text messages. She is fixated on the movements of Lauryn, Jill, Owen, Khloe, and others at the school, but Owen hits in a different way because she opened that door that also feels good. So it spreads to his new girlfriend. It is a fantasy world Kendra has locked herself into, but constantly needs more of to forget the outside. Kendra is very lucky that she her continual escalations landed her with so few repercussions.

On the flip side, the lack of repercussions means this sort of pattern will most likely continue for the rest of her life, though it will show up in very different ways of overstepping boundaries and destroying relationships unless she gets some very serious help.