。
She's been frail since birth.
Literal
She [topic-は] by-nature weak is.
弱い (よわい) means 'weak' or 'frail.' Combined with 生まれつき, it indicates she has always been physically delicate. The plain present tense 弱い states this as a continuing fact. In Japanese, this kind of direct statement about someone's constitution is more common and less blunt than it might sound in English.