Blooming baby bath

Tiaa
Soooo i bought the blooming baby bath for my newborn and she absolutely loves it. Its soft and comfy and really snug for her to just lay in and enjoy bath time...on the other hand my fiances grandmother (who we live with btw) insists that the blooming baby bath is a dirty alternative because she thinks it traps dirt...which it doesnt its completley safe . you use it then wash it and dry it. It stays soft and dries out really good because of the material its made of ( polyurethane foam). I also have a brand new tub for infants i have not used...which is the 4MOMS infant bath tub with thermometer and water cleaner..its huge and feels extremely tough for my babygirl. I feel she is too fragile to be using such a hard tub at this early of an age.(1month 5 days)...point of this post is .. The grandparents keep fighting with me to switch tubs..as if i dont know whats good for my baby.. And also does anyone else have blooming bath ?? ..& why do other family members tend to feel like they know whats best ..i understand elders are wose they know alot more but its 2017 times have changed..things evolved. No disrespect...im just not oldfashioned...im 19 but ive done alot of reading thru my pregnancy about the babys first year & learned alot but they cant seem to respect that.. What do i do??? I want to start back work and i cant because im extremely umcomfortable about leaving her here with them because i know they will go against what i say anyways 😒😞😞