Mara, often short for Mara-Papiyas, is the lord of the sixth heaven of the Desire Realm and the head of gods in Mount Meru. It is said that if a man could reach beyond the sixth heaven, he will then overcome all kinds of desires and delusions to go on the path to enlightenment. So there is only a line between the Buddha and the devil!
Her actions overall make sense, his do not. Dude has been saying she's nothing to him, so why would she assume otherwise? Like seriously, use an ounce of sense.