Well, she is a core contributor to Tor, but I don't see any possible reason why the FBI could not say that they just wanted to ask her a couple of questions about Tor to her lawyer(s).

I've been following her on Twitter for a couple of months now, and from me "getting to know her" from social media and her blog, I don't see a possible legal reason to ask her a few questions that could not be shared with her lawyer. After all, like she stated, her work is very transparent, so everything she's working on is available to the public.