This thread has been really bothering me, I know in AIBU it's impossible to really understand the whole situation and everyone will read between the lines in different ways depending on their life experiences, based on my own experience I just can't see how anyone would start a thread like this unless they were vindictive or very, very thoughtless.
I've been the subject of a bitchy 'why wasn't new mum more hospitable' thread, I was very fortunate in that I only found it years later and didn't stumble across it when I first discovered MN, which happened because I was googling post-natal depression/ baby constantly crying, at the same time as the thread was posted, I think that may go some way to explaining my supposedly poor hostess skills 
. Even reading it a long time after the event was horrible, it hurt a bit less because some of the details were embellished, and it was the made up bits that were called unreasonable, rather than things I'd really done/not done.
To me the 'friend' who is the subject of this thread sounds very vulnerable, new mum, partner already an ex (I know for some people this works out fine but I can see it as being likely to make having a new baby more tense and stressful), your OP says she's in 'a position to need a little help'. So why not help her out, instead of bitching about her in a very public place (and one often frequented by new mums who are struggling a bit), with so many details she's obviously identifiable to herself, and quite possibly any other mutual friends/ acquaintances.
I stand by what I already said about 2 bottles of champagne looking like an expectation of a jolly piss-up and it doesn't strike me as a thoughtful thing to take to a new mum.
It's possible your friend thinks that you think of her as some kind of charity case and that's why she felt the need to point out she already had a sling/ didn't need the baby clothes (even though a sling strikes me as a very thoughtful and generous gift), it's possible she just phrased things very badly as she's not in a good place right now, it's possible she really is ungrateful. I don't know, and none of the other people reading this thread can know for certain either, who WBU. What can be said with absolute certainty is that anyone starting a thread like this has poor manners and is totally thoughtless about the harm it could do to the person being bitched about.
Sorry this is such an essay but it's really brought the whole thing back for me, I didn't realise quite how much it still effected me until I saw this thread. I wanted to just write a wildly abusive post telling you what a rubbish friend you are, but I hope by explaining where I'm coming from I can give you a bit more insight into how it feels to be on the receiving end of something like this and how your friend might feel, if she ever saw what you'd said about her.