Too many complications.
BUT, what if SOMEONE, that was invited to hookup with Brenda, but didn't get to, because of change of plans, whose wife was gone, went instead to the VD's around 11pm, 12 pm.
Damon maybe wasn't home.
THis person , for whatever reason, pals up with Danielle. Maybe the boys were asleep, but she woke up to go to the bathroom. This guy, let's say, has a key. HE walks in and plays with Danielle for a bit. She is in these shortop and bottom pj's and is growing fast for her age. He kinda gets aroused, and starts getting handsier and handsier. Wants to play some 'games'. ... da...da..d.a.
Then , Danielle gets hostile, realizes he is touching her places he isn't supposed to. She resists, he grabs harder. Struggle, something, all of a sudden, he goes out of control and rapes her, or kills her.
NOW, the details, whether he takes her out of the house, or Damon comes home and helps him (probably) don't matter too much.
What does is what happens later. Now, Damon and Brenda have the goods on this guy. They can blackmail him.
New car, fine. New house, no problem, he's a mortgage broker.
The reason the partiers stories dont' match, is because Damon had to inform Brenda, and then they had to act like Danielle was there until morning. When things could be set up better and they could call the police, and the blackmailee could be home, safe and sound.