Which of my 2 female mice is the "alpha"?

Hi everyone,

I have 2 female mice, one black and white (Winnie) and one cream (Georgette). Winnie frequently grooms Georgette (who sometimes squeaks while she's being groomed).

Georgette never grooms Winnie, it's always the other way around.

Which one of them is the more dominant one, the one grooming or the one being groomed? Is there a way to tell from this interaction? They're both intact females, about 6 months old. They're the only ones in their cage.

Thank you :)