。
She tried to do something beyond her ability and was laughed at.
Literal
She [topic-は] ability exceeding thing [object-を] do [tried to-ようとして] was-laughed-at.
手に余る (てにあまる) means 'beyond one's ability' or 'more than one can handle' — literally 'to overflow from one's hands.' The ~ようとして (trying to) connects to 笑われた (was laughed at) — she attempted something too difficult and was mocked for it. The passive 笑われた is adversative: being laughed at is something that happened to her detriment.