Honestly, from what you have said here, I think it's all you. Bear with me here, I'm not being mean.....
She is just going about her business as an excited, first time mom. She does things differently than you. You are the kind of person who would have been frugal had you given birth, correct? She is not.
I don't think her comments have anything at all to do with you or judgement toward you. She is all about
her right now. We all know how that is....whether it's our graduation, wedding, children etc...we get so wrapped up in ourselves, we aren't thinking about how other people do, or did, things.
As for the finances, those are her business and she and her family are the ones who need to live with those decisions.
You mentioned you may have some unconscious bitterness. I would call it unresolved regret. Be gentle on yourself, and your friend. Focus on the fact that you both are able to create happy, healthy families, in your different ways, and let the rest go.