I came on this board searching because my daughter, who is also 4, has been masturbating or "wiggling because it tickles" as she calls it when I ask her about it. I found that it is normal for this to be going on and normal for children to want to look and compare with other boys/girls. Have you talked with her about it and had the conversation of who can touch her and so forth.
I know it is strange to see our little girls doing this, I haven't even spoken to my husband about it yet because he is going to have a hard time dealing more than me. LOL
Good luck.
i came to this website because I think my 3 year old son his masterbating. but with his anus! I also have a daughter who is 61/2 and when I ask her about her wiggling, she says the same thing 'it tickles". She's been doing this since she was 3. I just pretend like it's no big deal and swiftly tell her to do this by herself and I move on with what were doing. There has been no problem at all, so don't worry, its all completely normal, now my son on the otherhand...HA!
Well you may think it's wrong but it's not it is perfectly normal she is very young she doesn't know if it's wrong to like a girl she just thinks that there pretty and likes them i did it when i was young out 31/3 so it's normal I guarantee you every thing is normal just keep what you were doing!!
this is an article I found when searching for answers to a similar problem (except mine just turned 8) and just thought Id share
http://www.sfgate.com/cgi-bin/blogs/sfmoms/detail?entry_id=34323
You are ascribing adult sexual behavior to a four-year old. That is where you are wrong. She is not indulging in adult sexual behavior, but the touchy-feely curiosity of a very young child. However, you don't want her to display herself or her little friends since this could cause many problems socially. I would tell her that "ladies" don't do that. And make sure she keeps her underwear on.