A key point here, which the judge brought up with the ICE agents, is that they only had an "administrative warrant".[1] An “ICE warrant” is not a real warrant. It is not reviewed by a judge or any neutral party to determine if it is based on probable cause. "An immigration officer from ICE or CBP may not enter any nonpublic areas—or areas that are not freely accessible to the public and hence carry a higher expectati…
1) knowledge of a government proceeding
2) action with intent to interfere with that proceeding
It doesn't especially matter in this case whether ICE was entitled to enter the courtroom because she's not being charged for refusing to allow them entry to the room. The allegation is that upon finding out about their warrant she canceled the hearing and led the defendant out a door that he would not customarily use. Allegedly she did so with the intent of helping him to avoid the officers she knew were there to arrest him.
The government has to prove intent here, which as some have noted is difficult, but if the facts as recounted in the news stories are all true it doesn't seem that it would be overwhelmingly difficult to prove that she intentionally took action (2) to thwart an arrest that she knew was imminent (1).