So Clarisee is debauchering her nephews because they have feelings for the man she wants for her own. That is pettiness. And will not get her any closer to Lug at all.
But that is her own hubris talking as she thinks that Lug would ever fall for her when he clearly does not feel the slightest bit. And should her machinations ever come out (mommy Matriarch is sure to get behind it when if the timid Theo suddenly changes) she will loose him forever as he sees both Stephan and Theo as his brothers.