In law's Visitor Visa

I hope someone can give me some suggestions on my in law's Canadian visa application. Thank you very much in advance for any advice. Our situation is a bit complicated. My hu*****and and I just got the Immigration visa in November. Our baby was born in Canada last year and currently she lives with my hu*****and in China. I am studying in Canada now and would like to bring the baby back here at the end of this year. My mother in law applied for the visitor's visa last year and was rejected twice. What would be a valid reason for her to get the visa this time? Any good idea? Thanks!