If she looked 17 five years ago, probably not. There are people in their older teens who look like they're in their 20s, but not that many 12 year olds who look like adults.
When I'm sick, I sleep as much as possible, or just lay in bed if I'm not sleepy. I might read, drink hot tea, or eat chicken soup. If you're too sick to work, you should probably rest so you can get better.
You might want to look at LACT or CoolerControl? I don't use Debian, but if either of those is available in a form you can use, they should allow you to change fan speeds, power draw, voltage, etc. Or gamemoded can be used to force a game to use a limited number of cores, which can help reduce heat generation.
If she looked 17 five years ago, probably not. There are people in their older teens who look like they're in their 20s, but not that many 12 year olds who look like adults.