For a woman the requirement of consecutive fasting for kaffarah is not violated when she is prevented from fasting due to menstruation. So she will pause fasting in her period and then continue after it is over.
الحيض لا يقطع التتابع في صوم كفارة القتل والوقاع في رمضان إن لزمتها كفارة
— Nawawi - Rawdat al-Talibeen
If you are thinking of taking load with interest then don't take it no matter what. But if you have already taken the load and agreed to pay ribah then you have to pay it. Not paying after agreement is also sin.