@Eastie77 I had a friend do something similar recently; posted a picture on Facebook of them with a teeny tiny baby, and a caption along the lines of 'so I guess everyone should know this happened'.
She's a prolific poster, is very self absorbed, thinks she's absolutely gorgeous and is always posting about getting hit on literally (and I mean literally) everywhere she goes, and being asked by numerous modelling agencies to sign up and then following up with horrendously bad apparently professional shots of her. She's often been called out on by others because they know she's making it up. It's all a bit bonkers.
We used to work together and would go out drinking, and I always really liked her (and all her bonkers-ness), but we were never very close (weird jealousy issues on her part), so I would never have expected to be told about the pregnancy, but I thought it was a bit odd, partly that she had kept something a secret for so long, but mostly because I was sure I had seen her posting about nights out recently. I checked to see if maybe there were photos of her just drinking coke or something, but she's clearly drinking pints and getting pretty drunk at least once in each of the last 6 months of her pregnancy. I thought maybe it was an adoption, but then she posted about losing baby weight - only the once and she always advertises the new diet she's on, so I'm amazed she hasn't been posting her usual progress photos and statuses. And I know she knew she was pregnant, so knew she shouldn't be getting drunk, because she mentioned once about it being hard to keep it a secret 'all this time'.
After the first week the baby has never been mentioned again in any capacity, and she's not the type to keep any of her private life private. She's posted photos of her dog and said something like 'the most important man/the only man I need in my life' and I was  because the baby was a boy, but thought maybe she meant not including babies. Then she posted a picture of her best friend a few days later and said something along the lines of 'love this girl more than anyone else in the world' - I know it's just words and Facebook, but it still seems odd to me.
She got a few comment and likes - maybe around 25-30 - on her surprise announcement, but half of those were just question marks or people asking for an explanation, so not the massive fuss that normally follows a birth, so I do wonder if others are as sceptical about it as I am. It's very strange and I still have no idea if it's actually her baby 
@Ilovemycat2018 It does sound like it could be a weird jealousy thing. Maybe she feels like your grown up house buying overshadowed her pregnancy or something. Who knows.
If you otherwise like her, and this is the first time any sort of crack has shown in your friendship, I would just carry on as normal, and continue the friendship, but just keep your guard up a bit in case she does something weird again. It's hurtful and odd, but IMO not worth losing a friend over, if you are close enough to talk regularly and stay at her house far away.
I would ask again why you were singled out to not receive a phone call and have a surprise, in person announcement so much later than the others. Explain that you are a bit hurt and really confused because you would have been so happy for her and would have loved to have shared in the excitement with everyone else. See how she responds and take it from there