female cat doing spraying motions

Question
I have a small calico cat between 2-3 years old, who likes to come in the restroom with me when I am getting ready for work and such.  She is fixed and a good cat.  Always uses litter box.  We also have 3 other cats inside, 2 more females and 1 male, all fixed and get along.  When the small calico comes in the restroom with me, she does what I call her tail shake, she goes to the end of the bathtub and puts her hind end up by it and does this tail shake, like she is spraying!  But she does not spray anything.  She does this same motion all the time in the same place.  Never saw her do it anywhere else. just wondering what this could be?

Answer
Hi
my own cat does this and to be honest i have never really thought much about it.

i have always thought that it is a combination of scenting using glands near her rear end and also excitement.

if she does this every day, it has turned into a habit and she may not be doing anything at all. She is just used to doing it every day.

best wishes Kate