Trouble with sis in law.?

Hello all. Am currently married and just found out that I'm pregnant about 2 months plus. My husband and I decided not to inform anyone yet until a trip to the gynae. After that, we decided to share the good news with our folks, and since i was close to my brother, to let him and his wife know as well. His wife and I've had problems before. I have never met anyone like her, and the issues she comes up with are mind boggling, tho time and time again, I told myself to not get carried away with petty issues and be the bigger person. For a year now, we been getting along and I thank god there hasn't been any problems, for if there were, the whole family will be in turmoil. Anyway, after calling her up & telling her, her response was curt and odd, and she ended the conversation with a "congrats" and hung up. Now, I was a bit taken aback. It wasn't like her at all. But I thought perhaps she was busy. Yesterday, she called me up, cold and formal, and said "I'm calling you because your mum asked me to call you and ask how you're doing". I tried to sound friendly and unaffected, but worry was churning in my stomach like butter. I have no clue why she's acting like this, when i text-ed her to ask, she replied : "I will be as transparent and open to you as you are to me. Look after yourself and the baby." Someone, please, what did I do wrong now? Nothing i do is ever right. She always wants to play the big sister role, expecting me to tell her everything. Was she expecting me to tell her before I told my husband?? Was she expecting me to run to her for everything related to pregnancy since she had a child first? And after our last conversation, I don't even feel like going over. I'm utterly lost and confused. My husband doesn't know whats going on, he can't stand to see me bullied. I just want everyone to be happy.