Body piercings aren't meant to be. Your body probably isn't agreeing with what you're doing to it.
No, so i suggest that you go directly to a doctor; the piercing could become infected
-yellow/green discharge from piercing -pain or tenderness around the piercing -red, purple, or yellowish discoloration around piercing
Well if you are doing your aftercare correctly you should be getting the piercing wet every time you clean the piercing.
With tweezers or something that can grip the piercing.
As you would without a navel piercing, just be sure the navel piercing is the last thing you clean before you exit the bath.
Your question "Can navel piercing migration be down to growth" makes no sense.
She can still keep her navel piercing in.
3 to 6 months, depending on how it looks. If after 3 it looks nice and has no puss or discharge you can change it. If it still looks red or infected, I would wait another month or two.
Follow the written aftercare instructions provided to you by your professional body piercer. http://www.pacificbodyjewellery.com/aftercare/infected_piercing.htm
If it hangs or dangles chances are good that it will retain a piercing. Placing the navel piercing off to the side will be problematic for aftercare and irritation during the healing process. If you haven't had a navel piercing before then stay with something that is simpler to care for and will give a result a navel piercing is supposed to give.
It could become infected beneath the surface. Follow instructions carefully and seriously from your body piercer.
Navel piercing could cost anywhere between Rs 350 and 500 with navel jewelery done by experienced piercer.