She (and you) should be able to slip the clutch at least a little. It sounds like it’s engaging like a TM ICC motor does.
I’ll assume that there’s nothing physically interfering with it next to the seat or a bend in the cable housing itself entering the case. If it’s not the cable or something interfering with it physically, it might be time to dig inside the case to see what the actuator assembly looks like. If everything is in order, the pull of the cable should be almost buttery smooth.