Super frustrated with his family's opinion

So my SO family keeps telling me I'm not feeding my 3 month old enough because I'm breastfeeding exclusively. When I do pump she takes about 3 oz and they think I should start formula feeding because she should at the least take 4 oz. She is in the 70th percentile for weight and her pediatrician is happy with her growth. It really bothers me they feel this way because it makes me feel like they think I'm starving my daughter. Should I say something?