I'm an Iowa fan, so apply all the skepticism you want, but my interpretation was that Clark meant to move her arm out, but didn't mean to make contact with anyone. You can see the surprise on her face right after she makes contact.
Maybe I'm just overly clumsy, but I've had a few situations in life where I extend my arms to stretch and hit someone because I didn't realize they were nearby. I immediately turn in horror, which is what it looks like Clark did. I don't think Clark was stretching, but the horror reaction seemed similar.
FWIW I've seen some fans on Iowa boards claim an MSU player hit Clark's arm first and that's what led to the contact. I don't buy that argument. If that were true, I think Clark and Bluder would've mentioned it post-game.