"I never saw you as being a mum"

My cousin and I were really close when we were kids and we grew up apart now that we're older due to the fact that we live in different states and we have our own lives. We were talking and I told her that my husband and I are planing on having kids in our early 30s (I'm 26 and he's 25). She was surprised when I told her that and told me that she would never imagine me that I want to become a mother. She said she thought I'll be better off as a dog mum instead. After her comment, I've been feeling very down and now I'm questioning myself. She also told me that due to my thyroid issue (I have Hypothyroidism and Hashimoto's) I have a higher chance of having a risk pregnancy. Ever since our conversation I've been feeling very discouraged on having children. I would love to be a mum and be there for my children but what if I'm not good enough...?