I like to think of it like this. Aging is inevitable. You will age. But granted you don’t expose yourself to dangerous chemicals and stuff you shouldn’t be, treating your body right and you won’t age as fast or look as bad.
Yellowing of plastic is inevitable, as some of the chemicals do break down and decay. But things like sun exposure, cigarettes smoke and other chemicals would make the process faster. It will keep that glory white for a long time if you treat her right.
And I’m not sure if this is the correct answer, but I do not believe the chemicals used in scented ponies that cause damage can be transferred to others simply by being near them. But, I’m not a chemist. So uh...best to take that advice with a grain of salt.