Tis true. She only wanted to butter up Roxas so that he would go along with being asborbed into Sora without realizing he would no longer exist as an independent being. Namine speaking to Roxas was probably originally meant to Sora but you know Roxas, he thought that she was talking to him. She was like "Oh fuck it, I'll be with him."
lol
After all, Kairi and Sora are together at least in Kairi's eyes while Sora could see Namine when seeing her.
Wouldn't be surprised if Nami rewritten Roxas' memories of Xion with her