I am all for parents punishing their kids when the F up but I think yelling at your kid using the F bomb every other word is not the best way to deal a problem. All that does is teach your kid that is how to deal with the problem.
My daughter is 9.5 and I would ever talk to my kid that way. The reason I would never talk her that way is that my wife and I established the ground rules long ago and when our daughter makes a mistake we never have to yell at her to get her to understand her mistake.
My oldest is going to be 8 this year, so I'm not ignorant to the ways of children either. I also have spent the better part of the last decade in student ministries working with teenagers. Everyone is different, every child is different every circumstance is different. While I do agree with you, and understand your point, lets look at other variables here.
This little girl (at 14, yes, little girl) is sending and receiving sexual content. I agree her language is harsh, bordering on excessive for sure, but I cannot look you in the face and tell you with good conscience that I wouldn't flip my gasket either.
She won't win mother of the year, but I for one appreciate parents who take an active role in their child's upbringing and in this modern age, something like this might be exactly what this kid needed.
Mods please feel free to remove the post if its not completely in tune with the thread.