Discrimination?

Is it a real thing to be discriminated for having larger breasts? Because I'm fairly sure it has happened to me, a few months ago (I think around August). At my place of work, I was told I was not allowed to wear a vest top and to 'cover up', as I was 'showing too much off'. However, other girls who also worked there could wear vest tops, some of which were exposing more than I was (as in the top was pulled down lower). I feel like I was picked up on because I have bigger breasts than the other girls (I'm not showing off etc., here, simply stating a fact). I wore the vest as shown, with this cardigan.

I could have worn it a lot lower/pulled down, but I didn't, I also kept my cardigan on until I was made to change into another shirt (which had never happened with other employees, who I feel have shown off more than I have at certain times). I also only wore this outfit because it was what I was wearing when I was called into work to help out as they needed me earlier than expected and needed me asap, so I left the house in the clothes I was wearing, not feeling there were inappropriate.

This is not a complaint or dig at my workplace, but simply a question I was wondering about.