GUYS: is it possible for you to have a strictly platonic pretty female best friend?

My ex claimed his female friend was just platonic. They used to share an apartment together, just the two of them for a few years before he moved up near me. And then while we were going out, he went to visit her and stayed with her to hang out just the 2 of them for a few days before she moved further away. She knew about me. I just still wonder how they could only be platonic. He later did admit that she said she wondered about a relationship with him, she had some feelings, but he said it wouldn't work. He has other female friends as well -- more girl friends than guys. He'd mention this one friend a lot though, made some comparisons of me to her, and she was pretty. Is this something you guys would be able to do?