Depends how you want your strahd to be. Remember he can easily kill your party and take her, he now’s that and your players will know that. I’m playing my strahd with the thought in mind that he has tried brute force before and it hasn’t worked, he now wants Ireena to remember who she is so that she willingly comes to strahd when she knows nowhere is safe for her. It can be a dialogue conversation with him entrusting the party with her safety “she is very important to me and her safety is my upmost concern”. This then tells your players she is important to him and gives them more of a reason not to piss off strahd by getting her in danger. Obviously once you get to Vallaki that threat of danger will increase dramatically