The daughters played a very active role in Andrews feminization.
While I do think your theory is plausible and the sisters have certainly acted suspiciously throughout the entire story, I think you've got some facts wrong and have made some leaps of logic that I'm not seeing.
They didn't just create distance between Andrew and Marina from the get-go, acting as an in-between for them to communicate and effectively driving a wedge between them.
There's no direct evidence that they're intentionally driving a wedge between Andrew and Marina. Marina made the decision to go to Crete on her own based on Andrew's behavior, and she chose to leave her phone behind. When she returns to Athens, they're able to meet privately and visit the clinic together until Marina is called away by James (not the sisters). Andrew is then unconscious for 4 weeks, after which Marina visits him in the hospital where they come up with the plan to stay in character at all times unless one of them uses the earrings codeword. They then tell Nikos, Eva, and Sofia to adhere to this plan as well. Shortly after this, Andrew visits the salon with Angeliki, sees Gjoka, and loses his memories of his time in the hospital, including the codeword. This is what causes the breakdown in communication between him and Marina until he regains his memories. After sleeping with Nikos and regaining his memories, Andrew intentionally avoids Marina because he's ashamed of his actions and can't face her. She finally confronts him at the pool party, he admits to sleeping with Nikos, she storms off. Then the next time they see each other they fight again and she asks for a divorce.
The sisters may very well be responsible for steering events behind the scenes, and it does seem like they're very invested in the relationship between Nikos and Elena and don't care at all about the relationship between Marina and Andrew, but I don't see any
direct evidence of them intentionally trying to keep Andrew and Marina apart.
They're injecting botox and collagen-decreasing stuff in Andrews face to permanently age his face.
What they did was not permanent:
It wasn't until visiting the clinic that the doctor made permanent alterations to his skin:
This was not the reversible procedure that the sisters sent him to the clinic for in the first place. The doctor did way more than what the sisters proposed, and as of this latest update we now know he was paid to do this by whoever Seferi is talking to on the phone. It's entirely possible he's talking to one of the sisters, but perhaps not.
They gaslight Andrew into doubting himself about the drugs given to him at the party and Sofia even dodges the topic and wants to return to feminizing him asap (p. 172).
Gaslighting would imply that they know for a fact that he
was drugged and are trying to convince him otherwise. This could be the case, but it could also be as simple as they don't believe he was drugged because his story doesn't sound plausible. That's the same reason Marina didn't believe him at first.
Sofia also continuously gaslights Andrew into accepting his identity as their mother, just like Eva is.
This only seems like gaslighting until we learned that Andrew and Marina came up with a plan to strictly stay in character at all times and they instructed Nikos, Eva, and Sofia to do the same.
Sofia then lies on p. 253 about the message Marina sent.
What do you mean? What lie? She played the message for Andrew just a moment before she said that and it's exactly as she described:
Which is interesting as on page 831 it's clear there is some noise on the line when Marina tries to phone Sofia.
Again... what? I see nothing on that page that indicates noise on the line. And even if there was noise on the line, what are you inferring from that?
But anyway, I'm not really trying to debunk your theory, because I definitely think the sisters have some ulterior motive that is probably not in Andrew's best interest, and certainly not in Marina's best interest. But I'm not convinced they're working with any of the other conspirators (Seferi/Joel/Angeliki/Joanna/Mystery Phone Person).
