A Good Kind of Rebellion
Anastasia knows how stupid and reckless her escape with Lucien is, but since she's already on the roll, she might just have to convince herself that the probable consequences will not outweigh the benefits it will give to her friend.
She was not one to meddle in anyone's personal affairs. Perhaps, liking someone has changed her. But then again, she's always been the type who won't just stand around and watch a friend's pleas and calls for help.
As for Lucien, he may not have said it out loud, but Anastasia could clearly see how desperate he was at this point. Looking at his pictures for hours had probably helped her develop this sharp discernment. She can now read him with just one glance alone - know if his smile is a genuine one or a facade, and tell if he's saying the truth or not.