It's pretty common in games like this to have cat girls or cute cat monsters fight with fish, so it's not really indicative of one game or another. Although, in Monster Hunter, you make weapons and armor from the parts of the critters you murder, so it could be sort of throwing back to that. ...Kinda. Sorta.
As for Estelle, I'm thinking maybe she represents the Dragon Quest series? I'm not for sure though, I'm mostly going off the design of her shield and somewhat her armor.