See Igros Moshe (I believe) CH”M 2:12 (maybe 2:11?) in the bottom of the first paragraph where he mentions that a woman going outside not Tznius is an Issur Asei, and if I recall correctly he doesn’t mention Lifnei Iveir.
MDD: Even if there’s no Lifnei Iveir that doesn’t mean it’s Muttar.