My love, this is not about your low self-esteem, this is about you being unable to filter what is fact and how others want you to feel about yourself in comparison to them.
What SHE thinks is immaterial. Pity her that can't be pleased to see a child excel in something they love, poor her that can't be happy for a friend, or who measures herself by the achievement of someone elses child.
YOU are the star in your life, YOUR child is the one who matters here, and actually NOT having someone so poisonous and negative in your life will HELP you feel better about yourself.
Only have those people in your life who ADD to it. She can't be happy for you, for your child? move on. The joke is, her child could learn from yours, but this woman is too jealous and stupid to see it.
Screw her, forget her impending birth, sod the gift, she is not worth your time or thought. YOU are better than that, than her. she knows this.
Don't settle for the dregs of a friendship with a woman like her.