COS from H4 - F1 RFE

I received RFE for my COS application sayingt hat my payslips and bank statement is not sufficient evidence for financial ability. They asked my 3 months bank statements and other documentaiton and also reasons gfor sudden depoists of huge amounts in account. My problem is i dont have much amount in my account for last 3 months. I cna put amount today and then take bank statement and also can state a reason. Will that be fine or can I include my spouse sister who is resident at US as another sponsor as she have money and her W2 will also be provided along with mine.