。
She gladly lent a hand.
Literal
She [topic-は] gladly help [did-for-me-てくれた].
手助け ('help, assistance') is a noun built from 手 ('hand') + 助け ('aid'), used either as a noun (手助けを頼む 'ask for help') or as a する-verb (手助けする 'to help out'). It's the everyday counterpart to the slightly more formal 援助 or 支援. The ~てくれた marks the action as benefiting the speaker — without it, the sentence would say 'she helped' but wouldn't pin the help to the speaker. Combined with 喜んで, the sentence reads as a small expression of gratitude.