I don’t think Reinhard and Wilhelm made up, if anything their relationship is more hostile now than ever. Wilhelm called out to him using his name, asking Reinhard if he regretted his actions. After getting his answer, he turns his back to him and addresses him as “Sword Saint Reinhard-dono”, using a very formal tone and his title and tells him he has nothing more to say to him. He goes from trying to reach out to a family member to coldly addressing a title bearer, a title that he likely hates considering what is has done to his love. While he understands why Reinhard did what he did he cannot accept his answer and so tells him to effectively “get lost”, just in a more polite manner.