。
She was really pleased with my gift.
Literal
She [topic-は] my gift [object-を] greatly was-pleased [for my benefit-てくれた].
喜ぶ ('to be pleased, delighted') here takes its source of pleasure with を — a slight oddity, since the source isn't quite a direct object in the usual sense, but it's the standard frame: プレゼントを喜ぶ ('be pleased with the present'). 大変 ('greatly, extremely, very') intensifies the reaction. The benefactive ~てくれる is unusual on an emotion verb but does work here: framing her being pleased as something done for the speaker's benefit — capturing the speaker's appreciation for her positive response. A subtle but distinctly Japanese way of weaving gratitude into the description of someone else's emotion.