Are you seriously wondering what her problem is?
Why would you swear at your mother / while talking to her?
Have you no respect for her?
My daughter must try doing that! Hmph
In case I'm not very clear, your mother hates it because its disrespectful and you should not be talking to her like that.
Learn to use your words and show some respect. You're not talking to your peers, she's your mother.
And its perfectly ok if you don't perceive cussing as disrespectful, but then be respectful enough to understand that others do.