If you're running the latest (v0.3.5.2), Meredith will cycle through a few different activities each day in her bedroom, all in the Afternoon. The cycle rotates (predictably) through 1) trying on Lingerie (which you need to use the crack the door action to see, 2) sleeping in her bed, and 3) using her vibrator, if unlocked. Assuming you have unlocked the Good Vibrations!!! perk, you just need to try the next day and peek through her keyhole in the Afternoon.
As far as unlocking the bonus scene, if you've met the prerequisite, click on Meredith either in her closeup in the Kitchen in the morning or in the Evening & Night on the couch and you'll get a little VHS icon action. Use that to get credit for the bonus sex scene with her.