Now I'm not trying to say that how Frank handled Lilith was wrong. An overbearing stepdad would have been much worse for the harmony of the household than a doormat like Francis. Only that Shannon said out loud, to Frank's face, in front of all the kids, exactly what her problem with him was. Why would she lie? It also doesn't mean that she didn't harbor resentment toward Jessica, but we have to take a moment to see things from her perspective. She had beef with Jessica that had nothing to do with Frank. We don't know what that was, but for all we know Jessica bullied her rather than the other way around. Maybe her loathing of Jessica had a very good reason behind it, and her rival "trapping" Frank into marriage really stuck in her craw. From her perspective, Jessica took something that was hers when she had no choice but to move away with her family. She could have handled the breakup better, but she was a teenager. Teenagers never handle breakups well. Perhaps she thought the clean break was best for them both and didn't know how much she would miss Frank until it was too late. We assume that Jessica was an angel because she was pretty, but it has been my experience that sometimes the most beautiful people are the worst. We look at Jessica through Frank-colored lenses. Also, just because she had resentment doesn't mean she didn't love Frank and Abby. Lilith's story shows that it is possible for someone to feel multiple ways about a person at the same time. Nobody would deny that Shannon and Lilith are a lot alike. Maybe too alike. It isn't uncommon to not get along with a person because you are too much alike. It wouldn't surprise me to discover that Abby was actually Shannon's favorite daughter, resemblance or not, and that part of her jealousy about their relationship was that Abby would never be as close to her as she is to Frank. It's just that we will never know if we don't see her perspective. There is a lot of potential in Shannon's story. It would be disappointing to forgo all that potential to let her remain a wicked stepmother trope.
However, this also works the other way around. What we know about Shannon and Jessica's dynamic is this:
They both knew each other since first grade
Both could not stand each other to death
Jessica was the first in her age group to have sex, word got out, and was bullied by her peers about it. Especially Shannon, who, unlike the others, didn't stop when she had sex herself.
As far as that goes, I assume Shannon was probably interested in the same guy as Jessica, but in the end he chose the latter.
What we can definitely say: Abby is still intimidated by Shannon to the present (see the scene at the fast food restaurant) and the quote I referenced is a one to one from Shannon's biography page. Consequently:
Yes she tried to be a mother to Abby, but she looked more and more like Jessica and began to despise Frank for his marriage to Jessica and that he apparently had a child with her.
I'm strongly inclined to see the arcs as definitely canonical content, since they contain information that Frank can't know, such as Meiko's parents having tried to set Meiko up before, where she stood up to her parents for the first time, which Frank had just learned in the last update.
What information do we now have about Shannon and her interaction with her daughters and Abby?
Becca; "Her relationship with her sisters ranges from friendly to hostile, with her mother mostly hostile."
Yes, I admit that I, too, trust her to have her fingers in certain events and at least to be involved in the phone call that made sure Frank knew about the affair.
Abby: "Her relationship with her step mother is a bit more mixed. When her father married Shannon she was very warm and welcoming, but as Abigail grew older Shannon became more distant and cold towards her. Now that Shannon and her father are getting divorced their relationship is even more strained."
Here we see what Shannon's bio already says and I have credited her with in the past: She tried to be a good mother (to Abby) but with the resemblance to her birth mother that Abby developed, that ended. That definitely does not speak to me that she may have been Shannon's favorite child. Especially since she is a daddy's girl and she gave her similar evil looks as Lilli has done to Frank in the past.
Regarding her dynamic with Lilli, I have an assumption based on Lilli's bio:
"She was never very good with school work and dropped out in the eleventh grade. Since then she has been working at a local coffee shop."
Since she failed in school and had a job that was a dead-end job, I assume she thought her daughter was a failure. Although this is not necessarily true, after all we have seen little of the conflicts between the two ladies so far, but when I look at the dream at the end of Lilith's Longing, it is at least reasonable to assume that Lilli feels the same way, or at least similar.
Regarding her issues with Abby, it's pretty obvious that Shannon is a woman who clings to resentment. Jessica has been dead for years and yet she can't put whatever the problem was between them behind her.
In addition, one more thing: Shannon is 39, Becca is 23, which means that unless CNG made a gross blunder with the ages, she must have had Becca at about 16. If we assume that Becca was conceived in June (I'm assuming 9 months, since she was born on March 15 - which I think is an extremely hilarious coincidence in terms of the Ides of March) depending on when Shannon had to move in with her aunt (I don't know the exact month now) will have either been pregnant already or shortly after she moved there. If we assume that Becca is not Frank's daughter, then that leaves only 2 options:
1. Shannon already had a fling when she dated Frank and got pregnant, which would then be the cause for the move.
2. she took comfort elsewhere after settling down.
Since the detection of a pregnancy can take a while, actually only option 2 remains.
Has now nothing to do with the actual thing, but is an interesting fact and Becca's birthday is symbolically quite interesting.
What also makes me doubt Shannon's personality: She will surely have known how much Lilli suffered from her father's absence and yet she didn't think it necessary to inform her daughter that she had contact with her father, neither before nor after the divorce. However, I will give credit here that the whole affair story was a very spontaneous story and therefore she never had the opportunity to inform Lilli and possibly worried that their relationship would deteriorate even further.
However, I have my doubts at least about the last part, because even though Lilli's bio reveals little about the dynamics with her mother, there is one crucial sentence: "She is considered the black sheep of the family". We don't know who views her that way, but for me, in terms of Lilith's history and Shannon's career, Shannon is indeed the favorite in that suspicion.