Yea you pretty much nailed my initial thoughts. My train of thought was Ian only met her once at Fortress and that one time he said good morning to her. All the arguments like Louise is needy, easily manipulated, are perfectly valid, but I was basing my expectations on what Ian saw and knew about Louise. And what Ian saw wasnt imo enough for the sexting to move along from 0 - 100 like it did.IMO, it would only make sense if the threesome happened and Lena doesn't dominate Louise. That the only requisite for her messaging you nudes it's telling her that you like her style and the first Twilight movie is pretty ridiculous. But at the end of the day, this is a porn game so it's what it is. Also, I'm not complaining, fucking Louise behind Lena's back would be hot.
It happens also if Lena doesn't fuck Axel, the only thing that matters is you having a higher than 4 relationship with Louise. And as I said, you get that just by telling her that you like her style (the default 3 + 2 for choosing that option).
Maybe Ian could have dropped a line like "I wasnt expecting you to message me" or "we never really talked before". Just something that would make me believe they arent that familar with each other. But youre right, it's a porn game and it is what it is. It was just my two cents that the sexting scene seemed odd.