。
She worked for me.
Literal
She [topic-は] my [for-the-sake-of-ために] worked [for-me-くれた].
私のために is the standard 'for my sake / on my behalf' phrase, formed from 私の + ため ('sake, benefit') + に. It can mean either 'for my benefit' (purposive) or 'because of me' (causal) depending on context — here clearly the former. Combined with the benefactive くれた, the 'on my behalf' is doubled: she chose to do it for me, and it was a gift to me. Two layers of beneficiary marking is characteristic of Japanese, where the speaker's relation to events is grammatically encoded.