It is not like you got a bad reaction, it was just not the great reaction you were hoping for. If she was competitive over the engagements and weddings as you say, you can bet that she has been trying to conceive when she suspected you were, especially with the miscarriage (whether or not she had been discussing it with your MIL). So you have beaten her too it again. You should have anticipated that you would not get a great reaction again. Her asking about the gender of the baby was showing an interest, regardless of her intention behind that interest. For all you know she might be in the early stages of pregnancy herself and worried about miscarriage.....
My MIL and FIL actually gave horrible responses to each of my pregnancy announcements. First one, "oh, ok" , followed with my FIL having a heart attack 2 hours later! The second "really shouldn't you have thought about money before getting pregnant again" and then the third "well don't expect us to babysit, we can only manage two."
In reality my PILs could not cope with pregnancy announcements, but love their grandchildren.
So with your situation, you need to not have high expectations of good reactions from your BIL and SIL, but also no more horrible texts to them, no matter how competitive they are being. And just in case they are suffering infertility - don't go rubbing your excitement in their faces! Keep that between your dh and yourself and anyone else who truly is interested.
Congratulations on your pregnancy, hope it all goes smoothly for you.