Step families

Hi y’all. My DH and I are trying to get pregnant with our second. He also has two kids from a previous marriage. Do you guys think we should have to tell the BM when we get pregnant? People keep asking me if she knows we’re trying and what we’re gonna tell her and I honestly just don’t see how it’s any of her business. She’s high conflict and gets pretty rude about things. I just don’t see how’s it’s her business. Opinions or experiences?