Answer: Ideally, it would be best if the bookkeeper could share with the liaison the list of students with outstanding fees, and the liaison could see if any McKinney-Vento students are on that list. Any student could miss a fee for any reason, so it may be less potentially stigmatizing for the liaison to see the fee list than for the bookkeeper to see the McKinney-Vento list.
However technically, the McKinney-Vento list could be shared with bookkeeper in this situation, because the bookkeeper meets the FERPA exception of being another school official with a legitimate educational interest in the information (in this case, she needs the information for the legitimate interest of covering McKinney-Vento students’ fees). More information is available here.