Advice about TTC coworker?

Hi all! I really need some advice. I work in a small office, maybe 30 of us. I want to keep my pregnancy a secret for a while but I’m worried about telling one coworker in particular. She has been struggling with infertility since before I started working there 6 years ago and is currently doing IVF. It’s no secret and she’s really upset about it (rightfully so). When it comes time to tell work, should I tell her excitedly like I would the rest of my coworkers, pull her aside and tell her privately and emphatically, or not mention it at all and let her find out on her own through the grapevine? Thanks in advance!