FISA warrant on her chauffeur, she is picked up in the collateral damage. Tough for Difi if she was unmasked as part of the espionage case!
That was years ago, not recently, I think.
http://thefederalist.com/2018/08/03/sen-dianne-feinsteins-personal-driver-20-years-chinese-spy/
5 years ago, to be precise. FBI came and told her about her driver. No FISA then, certainly too long ago to get a FISA warrant against anyone now, at least about that driver. Are there any other spies in her office?