Its a monster the size of a planet. Claras been lucky enough to obey her instinct to leg it, and could run and keep running. But for Clara, coming to find a person you care about is the most important act of love. She cares about the Doctor, and hell if shes going to let a monster the size of a planet scare her off. Also she learned to ride that space moped really fasttalk about a quick learner! If Clara hadnt been there, everyone would have been in a lot of trouble. Clara was able to figure out how to defeat the monster, was able to offer the story she carried with her to sate its appetite. Even the Doctor couldn't figure out how to beat it, but Clara gave it unlived days. And the way she murmurs and these are my Mums makes me tear up every time.