M.O.
What about getting OUT of the house one day with her, think of it as a "business lunch". Get away from the distractions and interruptions.
Ask her how things are going. Give her the chance to talk about if the job is what she expected and what she can handle. Then you can address any concerns she has and transition into some things you've noticed/seen slipping, without seeming critical.
Does she have any "time off" with NO responsibilities? Like one day just for herself with no laundry or tidying up? I think she IS entitled to that. We all need to destress/decompress...I think it makes us better and more focused when we come back.
If she is "off duty" with the kids, but still has household responsibilities (read NOT on her day off), then address those issues. "I need you to throw in a load of laundry WHILE you're online." Or "Take a break to ensure the kids' clothes are laid out for the next day and rooms are picked up before they go to bed."
I think that if you take a woman to woman "business" approach to this issue, you may find a more cooperative employee who sees open lines of communication rather than feeling like an indentured servant.
Just my input - I hope you find it helpful! Let us know what happens!
Sara