The description is half true. She was described as "frozen stiff", not "frozen solid". The former is what happens when your muscles are so cold that the chemical reactions required for movement slow akin to rigor mortis. If you have ever experienced the loss of hand dexterity which comes from cold arms you have experienced this effect. If she had actually been "frozen solid", as in a human popsicle, she would not have been able to breathe or maintain a heartbeat -- both of which she did.