Happygirlygirl – beautiful poem for a 13 year old! I am impressed.
Regarding the supermarket maaseh – if the girls didn’t do anything wrong they won’t be punished. But when someone does something wrong, they are punished. If a girl dresses untzniusly, she is responsible for causing others to do an aveira.
That being said, it’s also important to remember that there is another reason for being tznius. If girls realized how demeaning it is to dress untzniusly, they wouldn’t do it. If the girls realized how the boys think, they wouldn’t dress that way. Everyone should listen to Rav Orlofsky’s tape on platonic relationships. It’s about negiah, but I think the things he says apply to tznius as well.
good point about boys being tznius as well. But it’s still primarily a Mitzvah that belongs to us. Go us!!