Note that they did have gender markers. people of the time would be able to distinguish a girl's dress from a boy's dress. Kind of how you can tell a boy's pair of pants from a girl's pair of pants today.

Also, predominantly it was only the children of wealthy parents who could have 'children's' clothing. Children of the poor wore rags --anything available to them.

MUCH easier to change diapers that way.

Obviously your daughter is not old enough to pull off her own diaper. Once she reaches that stage some type of diaper cover is essential. It seems it takes them a lot longer to figure out how to pull pants down if there's a bulky diaper underneath...