IMNSHO, the best way is not to sugar coat it. Just come right out and say, “We’re sorry to have to say this, but you need to improve your hygene. You come to work smelling of cats, and soiled clothes. It’s affecting your co-workers, and making it unpleasant to be around you. If you are a shower at night person, I think you need to go to shower in morning, and you might want to put your laundry into dressers so the cats can’t get at it.”
It’s blunt, but it is honest. And it leaves no room for misinterpretation.
And, sad to say, I’d suggest documenting the event. If she does not, or can not, change her reek - you might have to consider firing her.
I’m not an HR type. I don’t own a business. I have been told I needed to shower more often, while I was in the Navy, though. (I was showering daily - I just really sweat a lot.) It’s embarrassing and humiliating - but it also made it clear to me that it really was a problem other people were having with me.