My MIL is always asking me if my baby (now 2 months old) is getting chunky. Why is this such a big deal? She’s gaining perfectly and eats well, why does she have to be chunky? Why is that so important?

Dumb question maybe. I don’t know why this offends me so much. My daughter is long and lean like myself. I was able to solely breastfeed for about 4 weeks then I started supplementing and my milk supply drastically decreased. Tried to build it back up now I am nursing once in the morning and the rest formula bottles. I wish I could breastfeed more but my baby gets frustrated by it now since my breasts lost so much mass. She has a hard time staying latched now.