。
That fragrance instantly excites her.
Literal
She [topic-は] that fragrance [because of-で] immediately gets-excited.
香り is the spelling reserved for pleasant aromas — distinct from 匂い (neutral 'smell') and 臭い (negative 'stink'). Built from 香 ('aromatic, fragrant'), the same kanji that appears in 香水 ('perfume') and 香道 ('the way of incense,' a traditional appreciation art). で marks the cause/trigger ('because of that fragrance'). 興奮する covers a broader range than English 'excite' — emotional thrill, agitation, or in some contexts arousal — with surrounding context disambiguating. The plain present frames the reaction as habitual.