I feel like a shitty mother

I was getting my hair done last week by my sil and we were talking about our kids. My 13 month old is petite for her age but she’s growing at her own rate. My sil’s kids are 18 months and 2 years old and are chunky little monsters. Her 18 month old is fitting into 5t clothes! Well my sil told me that one day when my mil was babysitting my daughter for me, she told my sil that I’m not feeding my daughter enough and that she’s too small. Instead of giving her my breast milk she gave her formula to help her gain weight. The entire time I was under the impression that my daughter was drinking my breast milk. I felt heartbroken. Now I look at pictures of my daughter and pictures of my niece and nephew and feel so shitty for a) feeling like I’m not doing enough and b) for even comparing my daughter to other children. My sil thankfully stood up for me and told her not to compare the kids and not to give her anything that I’ve said I’m not okay with. Still no longer trust my mil to babysit unless my sil is there.

My daughter at her 12 month appointment:

Crying while looking through pictures and videos and wanting to wake her up because I miss her cuddles 🥺