。
She's the kind of person who can endure any hardship.
Literal
She [topic-は] any hardship [to even-にも] can-endure person is.
耐えられる is the potential form of 耐える ('endure, withstand, bear') — 'can endure.' 耐える takes に for what is being endured, paralleling 苦しみに耐える ('endure suffering'). The whole modifying clause どんな苦難にも耐えられる ('can endure any hardship') describes 人 ('person'), with 彼女 then identified as that kind of person. 苦難 (くなん) is a slightly literary Sino-Japanese compound for hardship — heavier than 困難 ('difficulty') or 苦労 ('toil, struggle').