Yonks ago I was invited to the wedding of an old family friend, but my partner wasn't. In this case though I wasn't offended because they'd not only never met my partner, but they'd rung to apologise before sending out the invite and said that they would have loved for him to come, but they had had a really difficult time getting the numbers down and were on a really tight budget. I was friends with the groom and the bride had a huge family so they were all doing their best to make sure everybody was happy and they hoped that I'd understand. (I did - they were so sweet about it).

In your case though, even if there are practical/financial considerations that your friend has to make, she could have at least been a bit nicer about it.

Apart from anything, the wedding is a long distance away, and you are going to be taking a small baby. I don't think that your friend realises that it could be really inconvenient for you to go without your partner there to help out with bubba. Perhaps she'll change her mind if you tell her that you might not be able to make it on your own? And if she doesn't, then this also gives you a good excuse if you decide not to go without having to get into a fight about it.