There is no reason not to try. But, if your broody hen can accommodate three more eggs then add three unrefrigerated eggs. This way at least your chance of success is 50-50. Good luck!
Okay so I just put four eggs under Lil Bit...one looks like it may be at day 11 and the other three may be farther along or less who knows? My friends hen quit sitting so we are trying! He said one egg was fully developed chick inside!