Hmm. That’s a tough one. Can you just say something short like ... “actually, I support the McCain/Palin ticket, and expect she’ll do just fine. Invitation still open?
:))
That’s short, to the point w/o being “militant” about it, and puts the onus back on her.
In reality, since she is a friend, the above is the best reply. It's the one I would use.
But then, all my friends already know where I stand on the political spectrum.