I agree the MT would have avoided calling Jennifer -- but can also picture the 2 women handling arrangements for fD's visitation with the children.
I would guess that fD might have difficulty managing his anger over the phone, as he seemed to see the children (and the Farber money) as his possession? Would such a scheduling call be beneath fD's perceived self-importance? MT worked for FORE Group per media, perhaps setting appointments for fD was something she did?
Possibly under the guise of "if I know when he will be with his children, I know when to be elsewhere." (Could be canny advice from the Medicare fraudster who moved an entire legal team into her counseling office in order to hide her files.)
IMHO MT knew that the Farber money only came with the children, a motivation to keep whatever contact with fD that she could manage. Even if that meant speaking civilly to Jennifer or the nanny.
IDK. We've had too much time to create our own fan-fic options with this one.
Where is Jennifer???
jmho ymmv lrr