These are all very good ideas for the most part but I think people should clarify what is halacha and what is extra. All you have to do is cover A, B, C, and D and all the rest is chumros.
If instead of someone coming over to you and embarrassing you in public for wearing a short skirt or whatever, focus on the positive on what the girl is wearing and don’t mention the negative. Like, where do you find such tasteful clothing that is tsnius too?… If you build her up a little, she will want to live up to that standard.
If there were some tznius women who were with it and stylish so you had someone to look up to. So that it isn’t that being tznius is equated with frumpy.
As for the question as to why BY graduates and students don’t dress tzniusly, there could be a million different reasons. A few I could think of off bat is:
A) the BY just teaches stuff as rules, do this and do that and none of the beauty, so why should I?
B) A teacher or someone gives a speech that you’re gonna burn anyway and you aren’t frum if you are lenient in something. So their attitude is why do I have to do all this, I’m already gonna burn. (this does happen btw)
C) There are so many other areas that I have to work on, tznius I’ll do last.
What inspires me and makes the biggest impression on me is when people tell me what the outside world thinks of you when they see you dressed tzniusly. How special they think you are…