Baby grossed out?

I just attempted to BF my DD on my right breast (she's cluster feeding right now, so this is probably the fourth time within an hour and a half), and she put my nipple in her mouth, but then gave like a grossed out expression and "spit" it out. 😱 I've never seen her do that! I tried twice, and both times she gave the same expression. My boob is clean (I took a shower, and put on a clean tank, and she already successfully breastfed on that breast), so what could it be?