Explain to me why it matters at all whether she was a member of a party other than Republican at some time in the past. She's a Republican now, and she was a Republican when she ran for governor. Lots of people have changed parties (or belonged to NO party) at some time or another.
Put it this way. If Michelle Obama were a longtime member of a damn-America party I think we would be objecting, a little bit.
Every American was party-less...at one time.