If she is the principal applicant than she is allowed do landing with her children. Her husband do not need to be with her at the time of landing. Dependents can always join later or may not even join at all, doesn't matter.
Here ( To be very realistic ) one point to be noted, If she claimed points of her dependent for her FSWP application and she got separated while application was in process & her husband inform CIC before landing than her visa could be cancelled and she'll become a subject of five years ban from Canada ( for not informing CIC about her separation ). If the separation took place later the application was finalized than no problem at all. Whatever the case she should land with her child immediately without any delay and apply for PR card. Her dependent DO NOT need to be with her at the time of landing. After getting the PR card she can inform CIC about her separation along legal papers to cancel her dependents Visa.
Best of Luck