Guidance in this game is generally shit, but most likely you need to exhaust every option with her and go through Kelly's content at the college up until Brenda tells the MC about her step-dad taking increasingly skeevy photos of her, then break into their house at night to look at his phone and find the photos of her and Kelly, before the MC gets the idea to have Kelly help ease Brenda into the sleaze.
Something like that, anyway. This game is a painful illustration of all the ways a sandbox can go wrong. There's a good game here drowning in opaque, unintuitive gameplay and aimlessly clicking through days and areas hoping to trigger something new.
I've played through the lot (I think) and still haven't the faintest idea what affects employee efficiency. It's just something for the cunt from corporate to bitch about every Monday.