@icekatze : Her former boss come here hoping to get Leonard to attend the ball that most magicians skip out on due to past experiences.
He basically used Lily as bait, knowing she's unlikely to just walk off on him.
His goal is basically to mark which nobles might be related to the kidnapping of magic-capable children.
Obviously most of the nobles will want to make connection with someone as powerful as Leonard, potentially via marriage for that slight hope the child might inherit his magic power.
But if he shows up with a lady in tow, the...more sensible ones would take note and drop the idea of essentially telling him "Hey, would you like to cheat on your wife with another woman?"
So only those with more greed than logic would remain and these sort would be the more likely to dabble in illegal act like above.
As for the expect criticism bit...well, he's someone of high position, so whoever he bring can be expected to be judged whether she's worthy ofhim.
And the more malicious group might do those 'open gossip' to try and shame the girl into breaking up (y'know, THAT cliche with low self-esteem female lead)