。
She's a woman with a strong personality.
Literal
She [topic-は] strong personality [attributive-の] woman is.
強い性格の女性 packs a small modification chain: 強い (i-adjective 'strong') describes 性格 ('personality'), and の links the entire phrase 'strong personality' as an attribute of 女性 ('woman'). This 'X の Y' pattern is the regular way Japanese says 'a Y characterized by X' — 三人の子供 ('three children'), 緑の目の少女 ('a girl with green eyes'). 性格が強い is a positive description in modern Japan: assertive, decisive, not easily swayed — though it can also imply someone hard to argue with.