  We investigate the formation of edge states in graphene ribbons and flakes
with proximity induced valley-Zeeman and Rashba spin-orbit couplings in the
presence of a perpendicular magnetic field $B$. Two types of edges states
appear in the spin-orbit gap at the Fermi level at zero field: strongly
localized pseudohelical (intervalley) states and weakly localized intravalley
states. We show that if the magnetic field is stronger than a crossover field
$B_c$, which is a few mT for realistic systems such as graphene/WSe$_2$, only
the pseudohelical edge states remain in zigzag graphene ribbons; the
intravalley states disappear. The crossover is directly related to the closing
and reopening of the bulk gap formed between nonzero Landau levels. Remarkably,
in finite flakes the pseudohelical states undergo perfect reflection at the
armchair edges if $B > B_c$, forming standing waves at the zigzag edges. These
standing waves comprise two counterpropagating pseudohelical states, so while
they carry no charge current, they do carry (pure) spin current.
