Either the Earth-1 Marsden is also a disguised alien or she’s a legitimate human politician.
The very idea that Guggenheim and this creative team almost included Lynda Carter in the crossover could also have huge implications for the character on Supergirl.
If it’s the latter, that means there’s also a human Marsdin on Earth-38, a.k.a.
Did the being impersonating her and is now President of the United States do something to the real deal?