。
She mended her socks.
Literal
She [topic-は] socks [object-を] mended.
直す covers a sweeping range — fix, repair, mend, correct, redo. With 靴下 it's specifically about mending damage (a hole, a torn seam). With words it shifts to 'correct' (間違いを直す = 'fix a mistake'); with health it's 'cure' (体を直す = 'restore the body'). In modern Japan, the cultural emphasis on disposing of and replacing rather than repairing makes 靴下を直す a slightly old-fashioned action — the heyday of darning socks coincided with postwar scarcity, when household repairs were the norm.