To be fair this is true for most ACoC users
Luffy, Zoro, and the Gorosei all use ACoC infrequently like BM did.
BM just underestimated them. She knew she could tank PW and she did. But she didn’t expect Kid to not be down and to have a move capable of blasting her away. She also didn’t expect Law to be able to silence her and prevent her from calling her homies.