Just tell her that weaning from 3months is an outdated concept from the 50s and new research and guidelines say 6months is now reccomended
And if she still won't shush then kindly inform her that babies can easily go with milk alone until at least 9 months, sometimes even a year.
Don't let her pressure you hun, do what you're comfortable with!! (obviously if you wanna wean earlier than 6months, it's totally your choice too, the above sounds kinda harsh but it's to try and get her off your back lol) x