please dont treat the child like they are doing something so naughty it needs punishment, like a few have said it may be a medical thing. constipation is common at this age and a warm bath might help and that fact that she must be trying to get rid of it before leaving the bathroom means she is trying not to get caught,

it could be an issue where she needs to be allowed to get out of the bath to go to the toilet or even put a potty in there just incase but also explain that its not normally where people poo and it should not be a habit, if she is constipated a gentle laxative will help to initially start things off then make sure she drinks plenty more water and a couple of juices to help.

Hi
I agree
She is acting out something but as a punishment I would make her clean the bathtub to show her this is not acceptable.
Make her clean it first then disinfect it and explain that it is dangerous for other people to be exposed to her poos. 
Thats why we do them in a toilet and wash our hands well afterwards
After cleaning up after herself she may think twice about what she is doing
Just my thoughts
Luv Deb

Poor little girl! Have the parents had a calm talk to ask why? As the ladies have said,there is a problem and reassurance is needed. If she sees that acting out is handled by with holding or punishment the answer won't be given cause little ones fear so easily. She needs not to go further into herself she needs to be handled gently to find out the cause.

i dont think yelling or punishing her since shes 7 will get anywhere ,, i would have a talk to her and see if anythings bothering her . she might of smeared it also thinking that she could somewhat hide it ,, dont be hard on her try to find out whats going on in her life

I thoroughly agree with Emmysmum that this may be a physical problem.....the other thing that leaps to mind is that it may be an emotional problem.  The bowel is an area related to 'control' of the body.....there's a good reason why people who are 'uptight' or 'control freaks' are known as 'anally retentive'!!

If your niece is feeling 'out of control' in an area of her life, this may be an outward sign of some inward struggle or anxiety. Is everything alright in the family setting? How about school?

If everything else seems normal and she is an otherwise happy child, then a Dr's visit is probably needed. However, if there is any area of her life where you suspect there may be conflict or anxiety.....consider whether this behaviour could be some kind of cry for help.

When your niece comes round, be firm but understanding and see what she can tell you. I also think appropriate consequences should follow this sort of behaviour.  Rather than stopping pocket money which bears little relationship to the problem, suggest that she will only be allowed to shower rather than bath or perhaps bubbles could be witheld. Also, bathtime supervision may help........I always found it a good time for chatting with my daughter.

Good Luck!

Whilst this behaviour is unacceptable, it is completely normal. Sometimes children feel pain when going to the toilet normally or have problems with doing a number 2....belive it or not, a warm bath helps to relieve the pain of pooing and also helps to relax the muscles, including those of the bowel, making it easier for one to do a poo.
I would get it checked out by a doctor, as i don't know the situation.... ask mum if she's having problem doing a poo.... it might be your answer as to why!