You should be aware of two tricky little catches in the law (and remember that she's a 'limited public figure').
You look at somebody at a point in time. If she brought a defamation lawsuit against Rush Limbaugh, then it wouldn't matter at all what her status is now. What would matter is what her status was at the precise moment Rush made his first allegedly defamatory comment.
The second is that Rush isn't given 'credit' for any of the fame she has as a result of his comments. If you've watched enough crime shows on TV, then you've heard the expression 'fruit of the poisonous tree.'
Rush would not be allowed to say she was a public figure based on any of the attention he drew to her by his comments, or by the attention that came from the liberal reaction to his comments. That's the law; it's not something I made up.
She gets to start with a clean slate.
I think she was a limited public figure for purposes of the topic of women's contraceptive rights the moment she testifies, under something called the Gertz test - and she may have been a limited public figure since she got media attention for protesting a pro-choice display at Cornell.
But none of this after-the-fact attention counts at all under the law, when it comes to considering whether she was a limited public figure when Rush spoke about her.
Caveat: I am by no means a legal expert.
Your comment makes sense, but this interview was on Feb. 16. (before Rush's comments AFAIK). A timeline would help, but then isn't it true that a court would have to decide to what extent this interview made her a "public figure?" I think that judgment would involve a generous degree of opinion. Yes, facts matter too, but I don't think there is an exact mathematical measure of how much of a public figure she was before Rush made the S-word comment.
OK, putting on my political hat now. I will repeat the suggestion that Fluke, acting as the agent of deep-pocketed Leftist entities, could file a lawsuit even if she knew that she would almost certainly lose in court, with the following goals:
1) Try to gain public sympathy, especially if private investigators investigated her private life (needless to say, we know which side the MSM would take). Obama could make public statements, while working behind the scenes to "encourage" feminists, disguised as salt-of-the-earth mothers and daughters, to organize rallies.
2) Go for an out-of-court settlement. Try to make the legal proceedings as expensive as possible for Rush, both to make him settle, and to hurt him financially.