Why would a man lower his eyebrows in maybe disaproval if a woman does this?

She talks to him about her struggles with shyness in his office but finds it difficult to open up about the fact. This man is her young lecturer who has flirted with her often before. She says to lighten the mood and to ackowledge the seeming awkwardness of telling someone in a position of power her vulnerabilities (as she has a seminar with the man and is very nervous in them) that 'she apologies for these horrible revelations of insecurity'..the man then lowers his eyebrows for a split second like an automatic reaction of dislike or something..When she is just on her way out of the room he looks at her bosom from the side as she walks by?? Why would he have this look of dislike for what she said though? Did he not believe her insecurity was authentic as he finds her attractive? Did he not like putting herself down? Or is there some other hidden motive, perspective?