@THE:
I don't think Big Mam is Lola's mom.
If she were, Lola would be more likely to say something along of those lines: My mom is a Yonkou, or My mom is one of the four strongest pirates
Yeah, but we don't know how long Lola's been in thriller bark. It could've been before Big Mam became a yonkou.
It could be also similar to luffy not knowing Shanks position as one of the yonkou.
Plus I'd rather not believe Moria had kept a Yonkou's daughter for decades and everything's fine for him.
Simple. MoriaH doesn't Know Lola's connection (if any) with Big Mam, and Big Mam doesn't know where Lola is or what is she doing.