Why does my semen come out from my wife after sex?

How do you know it is semen coming out of her? When there is coitus both male and female have secretions and it is normal because the vaginal secretion by sexual stimulation allow easy passage of the penis is why foreplay is encouraged to reduce friction and painful coitus for the female. The fact that you wife has secretion after coitus does not mean it was semen coming out.

If it is not deposited deep inside- if she sits or stands right after sex it can happen