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Her perfume smells way too strong.
Literal
She [topic-は] perfume 's scent [subject-が] strong-too-much is.
~すぎ is the noun form of ~すぎる ('to do too much, to be too X'), used as a predicate or in casual evaluations: 高すぎ ('too expensive'), 食べすぎ ('eat too much'), きつすぎ ('too strong'). 香り ('scent, fragrance') is the elegant native word for pleasant smells, distinct from 臭い ('smell,' often unpleasant). きつい applied to scent means 'overpowering, harsh.' The whole sentence carries quiet criticism — too much of a good thing.