Is voltage divider applicable on circuits where there is no ground?
Yes. Consider a more general case and apply the superposition theorem:







simulate this circuit &ndash; Schematic created using CircuitLab

$$ V_o = V_o(V1) + V_o(V2) = V1 \frac{R2}{R1+R2} + V2 \frac{R1}{R1+R2}$$