I don't think she's frightening of being questioned. I'm assuming that as soon as she agreed that her name could be made public she signaled a willingness to be questioned on her story. Ever since her name became public she's been saying she's prepared to talk the FBI.
However, I don't know if she ever imagined that the questioning would be in front of Senate judiciary members and broadcast on multiple channels across the US in a hostile environment where half the members have already deemed her confused, lying or mistaken. Maybe she just figured that was a threshold too far. As I said earlier, given that she appears to have led an extremely private anonymous life until recently, maybe there was a limit to how far she was prepared to go.
Contact local Representative and tell her what happened to me - Check
Write letter to Senator telling her what happened to me - Check
Allow name to be made public - Check
Answer any questions law enforcement officials want to ask me about my accusations - Check
Testify on live TV and answer questions in a hostile, politically-charged environment - Pass