The position that Terezi puts herself in isn't the best. She had been counting on the woman to go down, perhaps to get her into another grappling match. But with the failed attempt at taking out her legs, Terezi finds herself in a precarious place at her opponent's feet.

Her gut instinct is to roll out of the way, but logically she knows that it won't stop the spear from skewering through her in some fashion. The only thing that she might prevent is gouging something serious--like her heart. She does it anyway, rolling to the side and bracing for the searing pain through something less vital--like her arm or shoulder, if she's lucky.