。
She's wearing a bridal-looking outfit.
Literal
She [topic-は] bride [like-のような] outfit [object-を] is-wearing.
X のような Y is the noun-modifying simile pattern: 'a Y like X.' ような is the attributive form of the auxiliary ようだ ('seems like, is like'); attached to a noun via の it lets you compare or describe by similarity. So 花嫁のような衣装 = 'a costume like a bride's' / 'bridal-looking attire.' 衣装 is a slightly ceremonial word for 'costume, attire' — more theatrical or formal than the everyday 服, which is why it suits this slightly suggestive description: it's not necessarily a wedding dress, just something that gives that impression.