What a strange case, thank you for writing about it! I have never heard about it before.
By all accounts D'Wanna loved her son and took good care of him - he was a happy child who did not look neglected or abused - but evidence seems to point to her having something to do with his disappearance.
One thing I find quite hard to believe is the fact D'Wanna said she looked for her son for two hours before calling security.
I think generally, when a mother loses a child in a crowded area, even just for a few minutes, she is frantic - screaming, calling his name, asking for help. A distressed mother running around and screaming for her child for two hours would have attracted the attention of other customers and probably security, and the surveillance footage would have shown it.
On the other hand, I don't believe her failing polygraph tests means much per se - polygraphs are not as reliable as people think they are and many countries do not permit their use for that exact reason. I also don't think D'Wan talking about going to the mall is particularly meaningful: he was just four, and maybe he just misinterpreted something his mom had said - or maybe he just wished it would happen because he hoped to get the new toys he wanted.