She usually has an opinion about whatever subject/topic/issue is 'under discussion'. [=being talked about]
The proposal is 'up for discussion' [=the proposal will be talked about] at today's meeting.
After much 'discussion' of the plan, the idea was rejected entirely.
(..) But allow me to convince you. And promise you, right here and now, no subject will ever be taboo. Except, of course, the subject that was just under discussion. The price you pay for bringing up either my Chinese or American heritage as a negative is, I collect your fucking head. (..)2003 Kill Bill: Vol. 1