I hated DARE class, but I think that was because it was way back when DARE was getting kickbacks from the tobacco companies and refused to talk about the dangers of smoking. I kept mentioning it and they kept telling me to shut up.
People on the autism spectrum often look young for their age, in fact. My husband and I were both frequently mistaken for high schoolers when we were in college.
At my college, though, whether you were a “senior” depended not on how many years you’d been there, but on how many classes you’d taken. By my second year, I had taken enough classes to be a senior, so I was actually a senior for four of the five years I spent at college.
So maybe Abby really isn’t as old as your average senior. That would also explain why she has been a senior for more than a year.