If her work permit is expired and she did not do anything about changing her status to visitor before it expired or apply to restore her status to visitor in the first 3 months after it expired, she is now out of status and might get deported. If she gets deported before the child is born, the child will of course not be a Canadian citizen.
If the child is born in Canada, it will be Canadian but that will not change anything about her status. If getting citizenship was as easy as having a baby here, I think a lot more people would be coming here to have babies.