In general, I also have to say that Becca's personality brings traits that I associate with two Decepticons: the cold calculating of Shockwave and a bit of the scheming of Starscream, especially if Becca caught her mother with Lilli's father. Essentially, I say I trust her to do a lot.
That Shannon was no saint, I think that's no surprise. My personal thesis is: when she dated Frank, she had a girls' night out that was high on percentage and ended for her either in a restroom or a back alley with a stranger.
My assumption with the household look was actually more related to Becca's plot. With Abby, I could imagine: Scenes explaining her relationship with Shannon and Lilly, Abby being approached by guys who are then scared away by Lilly, Abby, Becca and Big Daddy and a conversation about the feelings they have for Frank. Most importantly, I think the conversation between Lilly and Abby is addressed shortly after Lilly gave Frank the black eye.
As for Lilly protecting Frank from Abby, I don't think that's going to happen. Abby is more the Bumblebee of the sisters and probably more open to that sort of thing than we give her credit for: I wouldn't be surprised if she had no problem with it since she could theoretically have a threesome with Frank and Lilly. Also, if we consider that Abby is manipulative more like Becca (albeit with less experience) I would rather assume that she would manipulate Frank and Lilly to her liking with feigned outrage.
For my next part of the assumption, let's take Lilly as a template. Before the first scene with Lilly there was a big outburst with her in private: With Lilly it was after she learned that her boyfriend cheated on her and afterwards again when she learned that Shannon had the affair with her (Lilly's) father. Abby already had her emotional outburst when she learned the story about her mother and since I think she is more emotionally stable than Lilly I think that this one time will be enough. If anything, she will be upset about her biological father.
As for Lilly sharing Abby with Frank: In the last update, Lilly asked Frank for some tips on how to "do something good" for Abby. I think slowly but surely things like that are an indicator that she's ready to share Abby with Frank, as she realizes she's not losing either of them. The first time between Frank and Lilly was just a few days ago within the story and since then she has made some leaps character-wise. That being said, we also don't know what Becca is doing regarding this: she did have to promise to keep Abby out of it, but she never, if I recall correctly, promised not to maneuver Lilly into accepting Frank and Abby as one thing.
