Control isn't the issue. It's the actual power itself. Unless to have better control is to totally suppress and ignore her power..which, as characters, I assume they're all growing to learn that they can be used for good. After the cure is found, shouldn't they all realize that they're powers can be a good thing?
Like for example, if Lillian made rain fall from the sky because they were running out of water?
But if Susan says she has empathy, she should stick to empathy, which is strictly emotional. She wouldn't feel the physical symptoms of every person in near vicinity. That's overkill anyway, isn't it?
Now if she started describing how Maika was frustrated or disappointed about how he couldn't do much in his current physical condition, that would be empathy, but to feel nausea and lethargy would be like directly tapping into his nervous system, which empaths cannot do. It's just the definition of empathy. If she stuck to emotions, she could be useful and find joy in her gift, but to be constantly tapping into everyone's amygdala is not in the capabilities of an empath. That's all I'm saying. I just wanna make sure she doesn't have an awful time with character growth and stuff later on. Without being drugged up, she wouldn't be able to realistically withstand everyone's symptoms at once