I personally don't get/understand evening only invites and have never been to one, nor have I been invited to one either as all my friends are married now. I think if I ever got married I'd have a wedding with no evening invites option at all. I'm also not into cash bars etc but then I'm naturally generous and think certain rules are a bit silly and unfair to others. The last friends I know to get married had a smaller wedding as it was lockdown and she is more of a NDN than a friend anyway.
It is strange though how friendships ebb and flow and change over the years though and in theory you can invite anyone you like to any part of the wedding.
As @SabreIsMyFave and @ZipZapZoom have nailed it, the bride is self centred inviting you to the hen do and not to the wedding and not telling you beforehand she hasn't invited you to the main wedding.
The thing is now you have a few choices:
- Go to the evening wedding and say nothing, you'll probably feel resentful though of not going to the main wedding.
- Go to the evening wedding and say something beforehand, bride will probably feel pissed at you, you'll have said your piece, your friendship may not survive or it could survive but be on shaky ground or ok, depending on how both of you handle it.
- Not go at all and say nothing
- Not go at all and say something
If you do the last 2 bullets, you risk drama. Adding a bridezilla into that mix isn't going to end well, and you'll look like bad guy for starting drama, she won't and her behaviour will be excused.
You also want to think if you want to end 18 years of friendship or not as despite what happened over when you broke up with your ex and had a baby and weren't in contact with her (personally I think 2-3 weeks not texting someone is awful, just to let them know you're ok is nice/good but I can sort of see why you might not do this). From her POV, she might've always have felt a bit off with you over that time but never said anything.
You might also be the type (a bit like me) who blows up and calms down (has only been in recent years and was a pushover in my teens and 20s, less so in 20s) so she's never felt comfortable bringing this time up with you.
You also say you're a close friend rather than a best friend. Not saying that's right her delegating you to the evening wedding because of this, because it isn't but I used to class certain friends I got on with/was closer to as 'best' rather than 'close'. Now someone died when we were both in our early 30s, I'd seen her as more of a 'close' than 'best' friend but she always called me her 'best' friend, and I realise now, she actually was my 'best' friend (but I had a few others, as people tend to do).
Anyway you have a bit to think about, hope you get it sorted out with preferably as least drama as possible.