An unplanned pregnancy can be jarring. If she was on bcp, I can see why she'd be upset.
Maybe use the shower an opportunity to point out the blessing of a baby. The 20 year old college student daughter of my good friend is unexpectedly pregnant by her longtime boyfriend. My friend had a difficult time w the pregnancy at first, but I reminded her that she will adore the baby once he's here. It will be an opportunity for her second husband, who never had children, to experience an infant. She said my positive outlook had helped her feel excited about the baby.
Your friend will appreciate the fun and fellowship of the shower.