Announcing to friends...

Hello. I wasnt sure where to post, but anyway. One of my best friends has been struggling for a long time with relationships, infertility, etc. I didnt tell anyone that I was not on birth control, not preventing. In fact, we've told everyone we're done. We have two boys and definitely dont want a third boy hahaha. But it is what it is. Anyways!! I'm not sure how to announce that im pregnant, without hurting her feelings. I considered sending her a card or something saying "will you be my *auntie*?" And giving her an ultrasound picture or something. Or would that be weird?? I dont have any sisters and my fiance has two sisters, 1 of which is not very close and rarelysees us and his other is out of state. My friend and i barely see each other but we talk often. I just want be sensitive with my announcement and I'm than fine with her visiting when the baby is born, etc.