Well, we don't see it as "not okay" in our family. Our kid is often naked with other kids, of all genders, either getting dressed, taking a bath, changing clothes, in the bathroom etc, running naked in the sprinkler etc. So ds has had many opportunities to be naked with other kids. I'm not saying you *have* to let your kid be naked with other kids, but is pretty typical that they might be nude around one another.
If she'd like more exposure to other's naked bodies (i.e. if you don't have other kids at home, so she never gets a glimpse of a siblings nudity) there are age approriate books like "It's not the stork" and others, that show naked bodies. This would allow her to "explore" in a safe way and give you a concrete way to answer any questions she might have about people's bodies. I know "Its Not the Stork" has a section on "good touch, bad touch" although I don't remember if it has anything specifically about not showing body parts.