。
She is a lady who stands out even among ladies.
Literal
She [topic-は] ladies [among-の中でも] outstanding lady is.
~の中でも (even among) sets the comparison group and then highlights her as exceptional within it. 際立った (きわだった) is the past/attributive form of 際立つ (to stand out), modifying 淑女 — 'an outstanding lady.' 淑女 (しゅくじょ) is a fairly formal, literary word for a refined, graceful woman — more elevated than just 女性. The formal copula である at the end matches this elevated register.