1st Amendment issues are complex. The 1st Amendment allows the publication of truthful materials, legally obtained. However, there are some limits which center around whether she would be considered a public or private figure. A lot of that goes to defamation issues. Speech can be restricted if it incites immediate violence - so it would depend on what you say. If you say "Casey is at X," you're not inciting violence. However, if you say to a crowd of people, "Casey is right over there, let's go kick the sh%$ out of her!", you're getting closer to speech which may be restricted.
However, this is all about laws and police action which may lawfully restrict speech. There could very well be civil penalties (i.e., Casey or her estate could sue) if she were harmed or killed due to publication of her location.
Ultimately, I don't think it's illegal, but I also don't think it's in good taste. Half the issues in this entire fiasco have been caused by the media, at least in part.