Thank You, I take it Sandra has been to Melissa's house to play before, hard to believe that Melissa just up and decided to kill her, altho I believe Melissa was involved with her death somehow
This will probably sound weird but as far as motive, do you suppose Melissa might have been jealous of Sandra, because Sandra was cute, smart, lighthearted, happy, and popular? Obviously Melissa is none of those things--maybe Sandra was cuter and smarter than Melissa's daughter, too.
Then maybe there was some anger around the issue of picking up the toys, the reason Melissa gave for sending Sandra away? Melissa may have flipped out over that. Maybe she got mean and abusive with her daughter, and Sandra witnessed it.
Just theories.