how to announce pregnancy to single best friend?

Alex • Blessed to be mom to our miracle IUGR baby boy! I've never met someone as strong and brave as he is!
I want to tell one of my best friends about my pregnancy soon. She was our maid of honor at our wedding and I love her dearly. 
So because I love her, I want to announce it as sensitively as I can, since she was feeling a bit overwhelmed at the fact that a lot of her friends were getting married in 2016, and she was still single. She is dating someone, but they aren't very serious as of yet. I don't want her to feel like I'm abandoning her since I'm pregnant, and I still want her to know I want to still hang out! What's the best way to announce that she's gonna be an "aunt"?