"She wants me to visit on Sunday."
Translation:היא רוצָה שאני אבקר ביום ראשון.
I would usually say ביום ראשון. If I read היא רוצה שאני אבקר בראשון the first thing that would come to my head, without any context, would be she wants me to visit Rishon, as in Rishon Lezion. I'm not saying it's not correct, just I'm not sure it is common (maybe different linguistic communities).