Clitoris "grasping"

Over the weekend I was very lucky and enjoyed playing with a lovely lady and her bullet vibe, but I noticed that as I moved the vibe upwards (lady friend on her back) that her clit scrunched down just as the tip of the bullet moved towards it. Efectively her clit seems to be grasping at the vibe.

Anyone else seen or heard about this?

...its just good muscle control...

I used to have a lh pocket rocket and found that I could hold it in place without using my hands and just rocked my hips til I got where I needed to. Best £5 I ever spent though I had the old version and broke it. Ah well. Its easier going "hands free" with a bunny anyway.