I was never much for keeping my mouth shut when someone did stuff like that. I was on top of the situation before the instructor ever had a chance to.
Simply put - I got fed up, when the girls kept talking and talking I decided I was done with the asking - I was going to tell them, AND make a point doing it.
Not only did I shush them what I did was
Stand up in the middle of lecture - turned to them and loudly said - if you are not here to learn LEAVE because the rest of us are paying for education and your BS is all I'm hearing - and I'm NOT paying you for your BS. So SHUT UP or GET OUT!
I drew attention to myself, to them and to the situation all in one sitting. They shut up and were put on notice on the spot because the instructor said
This is not gradeschool ladies. If you want to waste your money fine - but the rest of the class is here to learn, so if you are not - leave.
One of them stormed out - never to be seen again. Her cohort didn't have anyone to talk to.
By second year - she tried REALLY hard to talk to other people, but no one was listening. Wonder why. She ended up dropping out the following semester because she couldn't hack it.
Try that on for size. Can't hurt and it does ALOT of good. At least it did for me and the other 30 people in my class that graduated last year
Good luck - grow a backbone and make a disruption. You'll be glad you did - and so will others.