Best way to break the news to SIL?

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So my SIL has been trying to get pregnant coming up on two years now. I got pregnant basically on my honeymoon and she was devastated to say the least. Unfortunately that ended in miscarriage. I am now 11 weeks with my rainbow baby and I’m dreading telling her but I want to announce to my family in a cute way. Maybe just bringing cookies to a family event that say we’re due in Dec. I plan on waiting until I’m showing to announce but my question is how should I tell her? Should I warn her in advance that I’m announcing to my family and if her and my brother want to “late” and miss the announcement that’s okay or should I just do it without warning them? I’m pretty sad that my happy news makes her so sad but I understand. I just want to preserve my relationship with her the best I can. Any advice is appreciated! Thank you in advance!