Is it obligatory for a woman to perform ghusl if a man's semen lands on her hand and she does not ejaculate, or is wudu' sufficient?

If a wife extracts her husband's semen with her hand, she is not required to perform ghusl (ritual bath) unless she experiences an emission (of her own fluid). She is only required to perform wudu' (ablution). If she discharges madhiy (pre-seminal fluid), she must also perform istinja' (washing of the private parts).