They already said earlier that they would accept a call. They changed their story to saying they'd really prefer to meet in person, but since they already admitted they'd accept a call then that should still work.

In any case, the point isn't to cooperate with the police. The point is to just find out what the heck the FBI actually wants. Finding out what they want doesn't mean actually giving them what it is they want. She could say upfront that she's not answering any questions and just wants to know what they want from her. If they won't tell her under those conditions, well, she's no worse off than she is today.