For a full-time mon, if she cooks 2 meals herself for his kid w/o a helper, it must be 辛苦 than 在職媽咪.
But if she buy take-away foods, she will be as comfortable as working mon.
For working mon, most of them have helpers, say grandmon/grandf/maid. She only needs to go to work. Houseworks will be left for the helpers. Then, working mon is not a hard task.