I think Big Mam and Nami are friends now.. since i'm pretty sure Captain lola is Mam's daughter.. so since they haven't shown ANYTHING since Big Mam's ship showed up, i'm thinking that Big Mam/Mom whatever is friends with them now..
that's just what i think..
cuz otherwise.. there's NO WAY the couple people on the Sunny could survive her attack.. she has a HUGE ship and her entire crew.. Sanji and brook and nami and momo.. there's no way they could survive a fight..