。
She handed me a sheet of paper.
Literal
She [topic-は] me [to-に] one-sheet [genitive-の] paper [object-を] hand-passed.
1枚の紙 ('one sheet of paper') uses the counter 枚, which covers flat, thin objects — paper, photos, plates, shirts, tickets, CDs. Notice the structure: 1枚 + の + 紙 — the counter expression precedes the noun via the attributive の. This is one valid pattern (the alternative is the floating quantifier: 紙を1枚, where the counter floats after the noun-particle pair). 手渡す ('to hand over directly,' 手 'hand' + 渡す 'pass') is a compact compound for the physical act of passing something hand-to-hand.