。
She gave her son far too much money.
Literal
She [topic-は] son [to-に] too-much large-quantity [genitive-の] money [object-を] gave.
あまりにも is an emphatic intensifier 'far too / excessively / too much by far,' stronger than the bare あまり (which often appears in negation) or とても. Often used with negative-evaluation adjectives or actions — 'too much,' 'excessively.' 与える ('to give, grant, provide') is more formal than あげる, often used in writing or for giving abstract things (chances, education, money in narrative). The sentence implies criticism of the giving — that the amount was inappropriate.