Need Some Tips On Cleaning/Reorganizing Someone Else's Home?

If I was you I would just stack things where they are in a very neat way. Like if you have 4 shampoo bottles on the bathroom counter I would scoot them all towards the back of the counter and put them in order from shortest to tallest. Then I would clean all the counter tops. If there are things on the ground I would put them in a place where you know she wouldn'tt mind them being. If it is going to be junky and cluttered at least it will be an organized clutter...