That's my recollection too. And this was after she had essentially stolen two years of Cole getting to father his child. Cole can seem to forgive her anything.
I feel for Luisa, not because she's right to yell at Cole - Cole is just the only person she CAN yell at. It's an unfair situation, and it's not his fault or her fault really. As for her wanting Allison to sign away her rights, I don't think she really thinks that's a viable plan or even that Allison would ever agree. She just wanted Cole to try, to prove to her that she means more than Allison to him. But she doesn't, unfortunately.
Allison definitely left out the "dry drowning" part of the story, and I think it's because she still feels guilty and didn't want Ben to judge her. Little does she know he's probably a hired assassin or something ridiculous.