how could she do that!! please read.(kinda long)

I had to come somewhere to vent!! I'm so mad and heartbroken!! so my step mother whom I'm not at all close to, I can't stand to be anywhere around her, but I try to get along with her for the sake of mine and my fathers relationship. Anyways I was previously pregnant 2 years ago and had a miscarriage and they didn't want anything to do with me so I cut them out of my life well we've been trying to work it out and we're still barley on speaking terms. so I'm now pregnant again and was waiting to tell people til I seen a heartbeat well I saw a heartbeat and decided to tell close friends and family. well I decided today I would tell my dad and his wife.. well I told them I don't plan to say anything til my second trimester especially after the first pregnancy was a miscarriage, well not even 5 mins of getting off the phone my step mother posted it all over Facebook for the world to see. I'm so mad I don't know what to do I think I might explode.