And if she's not...its really not the end of the world. Just need to exchange some clothes and get a new tin of paint
That's right! A few minor adjustments if you must, or you could leave the walls pink as a kind of anti - gender typecasting stance

Even though my scan said boy I still left tags on all the boys clothes so I could exchange them and only had gender neutral clothes washed and ready for the hospital JIC there was a mistake on the u/s. I was quietly hoping for a little girl in there though