。
She liked the dress a lot but didn't buy it.
Literal
She [topic-は] that dress [subject-が] very was-pleased-with [but-けれども] did-not-buy.
けれども is the formal-leaning 'but' — a conjunction connecting two clauses with the second as an unexpected counterpoint to the first. Casual speech contracts to けど, polite speech keeps けれども or けれど. The が under 気に入る here marks the dress as the pleased-with subject (parallel to 好き), not as a contrastive 'but' — Japanese reuses が for both functions, so context disambiguates. The pattern 'liked it very much but didn't buy' is a perfectly Japanese way of capturing budget-conscious window shopping.