I have a feeling that Lola is Big Mom's niece not her daughter... My reasoning? Lola and Big Mom look similar but not similar enough to be mother/daughter... And there's the fact that Big Mom is a giant evil acid drool dripping monster who would eat her subordinates whole for an afternoon snack.
Why do I say she's her niece??? I know One Piece isnt your typical story and its almost completely unpredictable but I would like to call forth the "Feuding Sisters" cliche. Big Mom is shown to be this grotesque mass of woman who's favorite past time is eating, eating, then eating some more with her subordinates appearing to share the same sentiment about food (except for Tamago who is concerned about their finances)... This quality, is not shared by Lola whatsoever, she was never shown having a powerful obsession with food like Big Mom nor the heinous and heartless qualities that Big Mom is infamous for... She has however, displayed an obsession with marriage and having a husband, I believe the reason for this os because her mother is married possibly to multiple male partners and Lola believes it is the most amazing thing in the world. Going along with that, I believe that Big Mom's hypothetical sister is far more attractive than her and because of this she is able to get almost anything she wants (similar to Hancock) while Big Mom has to work hard and ruthlessly to get what she wants.
The hypothetical feud between the sisters could be in regards to Lola's Mothers utter lack of responsibility and her laid back nature while Big Mom is hot-headed and brutal which has led to many confrontations between the two since they were kids. This feud could aid the Curly Pirates because Nami could accidentally use Lola's Vivre Card and reach her mother rather than Zou which will lead to a conflict between the two sisters, allowing the Strawhats time to escape to Zou.
All in all, I truly dont believe that Lola is Big Mom's daughter, their attitudes are completely different and Big Mom doesnt seem like someone who would protect a pirate crew without a business proposition which doesnt seem like something Lola would want to force upon her friend Namizo. I could be wrong, however...