She is discovering her body, don't worry, but don't scared her, keep an eye on her...and keep her away from older kids or other people that will take advantage of that situation certainly if she asks questions or talk about it.
it kinda depends i watch my 2 year old nephew's but it kinda depends if it a neighbor i think no but if it like grandparents or aunts or uncles ect.. then yes because you can trust them