I'm not a huge fan of Isabeau. There are a few things that contribute to this - 1. my 1 year old male cousin's name is
Beau, therefore I see the -beau as being masculine and 2. I am an
Isobel /
Isabel /
Isabelle etc fan and would prefer the isa-bell names anytime over Isabeau.
However I think it is very usual especially as a middle name and
Estella Isabeau is lovely