Idk because it's hard to pretend having an accident of you're in hospital. But yeah the frequency is making her obsessive
This actually aligns pretty well with how people with obsessive compulsive disorders sometimes believe if they don't do this very specific acting something bad will happen, and they use whatever they see as proof of their belief. If ha-im one days forgets to listen to the frequency she will be nervous and see any small thing as evidence that her boyfriend is cheating because she didn't use the frequency. Thou seeing how this manga is I think it probably has a mystic element
Did oppa really cheated on Da-in? And listening to the frequency only makes HER more obsessed with oppa than oppa to Da-in.