I did suggest the name Anneliese, DH liked it at first then said no.

BIL's DD is Ella and I hear them call her 'Ella Bella' so I am hoping that this is a good enough reason to say please do not call her Belle/a as her cousin is Ella.
Just like Matilda cannot have the nickname Tilli because she has a cousin Milli.

Thankyou for your input everyone.