ok. I'm going with chanel 5, we only know she is a legacy, but i think her dad is the district attorney who considered the melanie case closed.
Guessing gigi's plot is in revenge, marrying wes to get grace's inheritance money and related money being the kappa lawyer.
Chanel 5 watches dora the explorer which reinforces the kid thing we see with paper cutting we see in thanksgiving, and she likes rules, which is probably taught from a strict family.
ep 1. Only chanel 2, 3 or 5 was in the kitchen and could turn on the fryer to kill Mrs Bean but we don't see them overhearing chanel talking about frying Mrs Beans face in the coffee shop. They would've sent the pledge to look for a bowl in mrs beans room when they found the pictures which triggered events. 2 was sent up to find it. Boone kills deaf taylor swift, the victory punch after the head explodes is the same as chads during charades.
ep 2. her over-reaction to boone justifies boone's later comment of "am i meant to be scared?", referring to the last coffee shop scene with the chanels, not the outfit itself. And the start of him going rogue plan, which chanel 5 is pissed about.
ep 3. no proof for coney or the double red devil fight. trial of elimination suggests hester for the double red devili think, who i like to think might've been hiding in petes car with grace when they went out to find mandy to give incentive to think others know where mandy is now.
ep 4. boone went out to mandy at night.
ep 5. chanel 5 didn't get chanel out of jail. The lighters used to light the pumpkins at the maze are the ones zayday finds later in thanksgiving in the downstairs bathroom. Gigi turned on the lights. Chanel 5 is late at the end because I think boone might've used the downstairs and secret kappa bathtub now, which needs key access (key in chanel's closet desk, chanel 3 has one next episode so chanel 5 should have one). In the scene with sam next episode when she dies, the bathtub has more blood in it, the handles and shower hose attached suggesting it's been used compared to when we first see it with grace and chanel handleless and dried blood. With the lair compromised no-one would expect to look in the kappa house for the devil. The blood sam finds is actually red clay from boone.
ep 6. It's boone killing sam, he's been hiding down there, but he has to use the tunnels now that it's locked down for a panty raid (by chad or pete hacking caused it trying to perv on grace). Revealed in a conversation with 3, Chanel 5 is pissed both twins are now dead. She thought only one would die and probably had a deal and this is why she later turns on boone who fled to the gym.
ep.7. pointless with feather story, and producers officially dismissing supernatural elements. Hester was probably messing with the chanels on the Ouija board since her thing was correct. Good for hester, chathy theory fans.
ep 8. no proof of who or why Jenifer death. Don't think it was boone. Gigi is now the fiance, her plan was to get gace's inheritance from her mother's car crash. Her mother would've been loaded being a kappa.
ep 9. chanel 5 has taken things personally wants denise gone next. she left to give boone the plan. Now she's fed up with boone and chanel saying she didn't want a sisterhood she picks gigi over boone. All person bulletins that chanel 5 hears, and gigi comments on are only sent to police personnel though, but it's done via radio only which links them. Unless Gigi is listening to a police scanner. Plot hole.
ep 10. Chanel 5 likes rules to be followed; like the plan, the rules for house kappa, and is once disappointed again at gigi getting the wrong food. Chanel 5 remembers her really family and sister is chanel 3 who she made a pact with earlier to live longer than chanel. Chanel 5 switches the head with the turkey in front of 3, which she is ok with since it means she outlives chanel due to the pact they made before when chanel 5 was pissed both twins died.
Chanel 5 wanted it to be all over now, and did try to leave, but boone went after her and was convinced to go back.Boone still needed her for gigi and zayday romance help though.
edit: boone obviously kills caulfield so he leaves earlier than i say. I also think part of the plan was making sure chanel 5 became 1 and hooked up with chad for his inheritance.
Pushed so far, grace, zayday and pete plan to kill the chanels as their only chance of survival. WIth their lead to Gigi being the one to give the 95 story now gone, they have reason to suspect chanel and chad know more and are probably behind it.