One thing about people guessing a motive is we are coming at it from a non psychopath viewpoint.
So it's hard to get inside someone's head which is wired so different to the norm.
Psychopathy is linked to thrill-seeking, impaired capacities for empathy and remorse.
People with extreme variants of primary psychopathy often have all the traits of the "Dark Tetrad," including Machiavellianism, narcissism, and sadism.
In my opinion she may have had some sadistic pleasure in causing pain.
And then tricking everyone thinking she's smart enough to get away with it. She had a pleasure in thinking she was smart to "get away with it" She would manipulate staff etc.
She seemed very good at manipulation.
She imo, got some sort of pleasure in interaction with the parents straight afterwards, which imo is sadism again.