How do you think Diantha became a member of Team Magma?

We hear in the ending of Dating A Team Magma Girl (the first one), that Diantha herself was a member of Team Magma, but we aren't given how she became a member, or her rank. What do you think her rank was, and why did she join in the first place? It's not common for a Champion to become part of an organization like that, so let me know your stance!

~Aliana Akebi