you need to pay her since her visa issued, if you wish her to come on 1/3, you need her to take no-paid leave during that period, however you need to take responsibility of her during that period woh, you need to think about it. You can pay her salary 1 months after she come, if she come on 14/2, you need to pay her at 14/3, there no need to calculate from 1st of month.