。
She is a very wise mother.
Literal
She [topic-は] very wise mother is.
賢い is one of several i-adjectives for intelligence, leaning more toward 'wise / shrewd' than the academic 頭がいい. Calling someone a 賢い母親 frames their parenting as judicious and practical, with overtones of being able to handle whatever comes up — a culturally common compliment for mothers shaped by the long-running ideal of 良妻賢母 ('good wife, wise mother').