^The post does not say she prayed to help morning sickness, also, the auto-translation isn't really correct.
It says: "I went to a shrine, prayed for the health of the little ones and afterwards walked alongside a stream where the air was clear. It felt good" and then she was adding the hashtag #morningsicknessrelief
For me it reads more that the walk and the fresh air helped her with her morning sickness. Also, she does not talk about "babies" but about "chibi tachi". Chibi is usually either used for a short person or for small children. I guess she just prayed for the health of both of her children and is not having twins.