I’m not sure the issue is the source of the music as much as the type of music. There are some very nice songs whose sources are non-Jewish (the popular tune to Maoz Tzur, for example, is from a German folk song) and some tunes which have Jewish composers, but the beat and overall musical style are directed towards and speak to the most base, animalistic parts of the human soul (nefesh hab’hami).
I would assume that what you refer to is the latter, since unfortunately that’s what is popular today, even in our Bais Yaakovs.
I think it’s wonderful that before disclosing this information you are taking into consideration the possibility that it might violate the halachos of loshon horah and hurt someone’s parnassah.
I would think that there would have to be a toeles to be muttar, and that simply telling your friends that these songs have a non-Jewish source would be pointless. They would probably listen to them anyway, and if not these, others, which are just as bad, regardless of who the composer is.
If you do have some influence over your friends, the toeles I can think of is to use the fact that they are dancing to the same music as the lowest parts of society dance to, in their clubs and at their parties, to demonstrate how low we have fallen (at least in regard to our musical tastes).
A teacher who has the genuine respect of your classmates might have a better chance of presenting this argument in an appealing way which could have a positive influence.
Hatzlocha.