  In frustrated spin ladders the interplay of frustration and correlations
leads to the familiar Haldane (H) and rung-singlet (RS) phases. The nature of
the transition between these two phases is still under debate. In this paper we
tackle this issue using tools of quantum information theory. We consider
frustrated mixed-spin-(1, 1/2) ladders with antiferromagnetic leg, rung and
diagonal couplings, and calculate various quantities, such as the entanglement
entropy (EE), the Schmidt gap, and the level degeneracy of the entanglement
spectrum (ES). We use two numerical techniques, the infinite time-evolving
block decimation (iTEBD) and the density matrix renormalization group (DMRG).
We demonstrate that there exists an intermediate phase in which the ES levels
do not exhibit the characteristic degeneracies of the H and RS phases. To
understand the underlying physics in this phase, we investigate short-range
spin correlations along legs, rungs and diagonals and show that in this
intermediate phase long-wavelength modulations occur, akin to bond order waves.
