Thats a tough one Antheia- it reminds me of the bath scene in the 80's movie "look who's talking 2" when the two little kids are learning about penis's and vagina's!! And they were looking through the magazine and saying who had what (boys and girls etc)

I have all this to look forward to, so i havent got any first hand experience to pass on, my advice is to maybe use this as the opportunity to explain the difference between mummies boobies which no one see's in public and daddies boobies which sometimes people can see when he has his shirt off- like at the beach or on a really hot day- but that mummy and daddy are different- and Lily is like mummy- so she should keep her boobies to herself- IYKWIM LOL

I guess it depends too whether she has been a child encouraged to run around in a nappy and nothing else when its hot- or if she is used to being unclothed- (like many normal very young children) and i guess this is the transition change when she needs to learn modesty.... the only young girl i see alot is a friend of mines child and she is about 4 and she is quite shy when getting her bottoms off (having to change undies on etc) but she will happily walk around with no top on and thinks nothing of it as she has three older brothers who dont wear shirts and while she knows their "bottom bits" are different- being with her being 4- their chests arn't all that different IYKWIM
Her mum continuously tells her she should put some clothes on but if its hot she flatley refuses because "her boys" dont wear shirts!!

Well i guess i did have half hands on experience- but only to say- you might not be the only one- not any real answer to the question!! LOL

Good luck!!