Her ability is to create illusion that affects all 5 senses, when she touched Makoto and Yukiko they were already seeing what she wanted them to see (and page 1-6 is his illusion). She still killed everyone though just for safety (since the Patissier could have been watching) and because she didn't care about anyone but Haruhito and thought he would never figure it out within her illusion.
Which would happen, but Haruhito was suspicious and cut through his own eyes to see the reaction, but the preprogrammed illusions had naturally no reaction which allowed him to figure out that the entire escape plan and everyone involved were either a lie or already dead. At this point he knew she would keep killing everyone because of the rules of the city, the only escape possible would be death, which would at least save a few people (in particular Makoto and Yukiko, which she didn't kill immediately). It was their only way of escaping together.