It's not like that on the simp route(
), if you chose to spare her during your first fight. During the manison fight, he just cuts her eyes after stabbing her. He's leaves her there after he sees her memory. Her status isn't quite clear but the MC definitely didn't kill her there as getting her memories isn't a lethal thing. Only on the "kill" route during the first fight do you kill her brutally before leaving.
I think people are using Nico's statement of her saying she's going to retrieve the 3 corpses as a sign that Danica's dead but Nico doesn't know anything. She's just assuming they're dead because they lost. Now, I wouldn't be surprised if Nico herself killed or captured Danica even though the MC spared her.
Probably just have to wait until future updates to know for sure or just ask the Dev. If She's permanently dead then the Dev probably wouldn't mind telling if it's not plot related. For now though, her status is unknown and I'm on the side that she's still alive and most likely healed by now since it's been awhile, time wise.