Consider that student had had a strep throat two years ago, why would she develop it again?

Answer: Yes, a strep throat can reoccur in that student because of the factors like -

weak immune system resistance to antibiotic still persisting bacteria of strep throat etc.

Explanation: - Strep throat is the situation of the throat when it feels pains and inflammated. There are chances of the relapse of strep throat because of the weak immune system and does not complete course of antibiotics or has resistance towards it. The student can also catch the infection again and can still have presence of the bacteria of strep throat.