Too much transparency too little experience

I just spilled the beans on my coworker. They kept on asking me to keep their birthday a secret because they didn't want an awkward situation when their coworkers wanted to celebrate whilst she didn't want to throw a party.<br><br>I am newish in this company (2 months) and have barely spoken to my boss, whom I assumed would also naturally find out about my coworker's birthday from other coworkers. So it was hard to keep it a secret for long (especially considering the fact that I barely talk to her, only once in a while on a collaborative project and she's very reserved)<br><br>My boss wished me a happy birthday on my birthday, and I thought he was just a nice guy, and she didn't believe me that he didn't know it. She said our boss wasn't that great and she would know better.<br><br>So she kept on asking me to keep her birthday a secret, which is a bit awkward for me because I had barely spoken to her. She went on and on about how she didn't like being wished a happy birthday.<br><br>Then I got caught in other conversation and the boss said something about her birthday and he said "we'll throw a party" so I panicked and said "she didn't want to throw a party" and he was like "what, she doesn't want to throw a party?! She always throws a party!"<br><br>I don't know what to do. I am still in my probation period. I don't wanna be let go over something like this, but I also feel too bad to not tell her.<br><br>I will send her a message to apologise and see how she reacts. This is my first job, so I don't know if it's a big deal or not.