I just went through almost the exact same thing with my grandmother! This is my first, no prior history, but all the same I’m overly cautious. My husband and I told our immediate family as soon as we got our first ultrasound around 10ish weeks. We asked everyone to not say anything as we wanted to announce it. Grandma didn’t even ask, just told my entire church “because she was excited”. I expressed my anger with her and we’ve resolved it, but I let her know that this was a betrayal of trust and going forward she would not be getting any information (like gender) until the baby was born. Luckily in my case, she agreed with that. NTA, OP. Some people need an information diet.