There are various reasons why Hazel defecated on the couch right in front of you. She may be having an intestinal problem and just couldn't hold it, she may be stressed and felt she needed to mark territory. If any stray cats hang around your house, she can be picking up their scent and this give her the urge to 'mark;' it's instinctive.
Make sure to clean the soiled area with an enzyme based cleaner for pet stains and odors, like Nature's Miracle, Zero Odor, Odor Mute and many more, available at your pet supply store.
Also, you can get a Feliway plug in diffuser to help diminish any stress/anxiety she may be feeling. Here is more information:
It might be a stressful situation, that your daughter visits once or twice a week. The kittens may be confused why she's not staying and spending more time with them, if they're her cats. You have bonded with them more, because you are their primary caretaker and food source.
It would be a good idea to have Hazel seen by her vet and have a fresh fecal sample tested, to see if there are any intestinal parasites. Some are not visible with the naked eye, but must be seen under a microscope.
If you have only one litterbox, try adding a second one in a different location and this might help. Use an unscented scoopable litter and you might add some 'Cat Attract', a litter additive that contains herbal attractants which encourage use of the litterbox. Also, if she does it again, place the feces in the litterbox and show it to her, so she knows where it belongs, not on the couch.
I hope all will be well with Hazel and her sister!
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