What can I do to make this girl stop talking about me and my gf?

Her name is Ana. And she keeps talking smack bout me n my gf saying how I'm cheating on her whn I'm not. How I dnt let ma gf out. But we dnt feel like going out. How I waste ma gf money. Whn for wat I got ma money too. And she keeps talking bout more stuff. But how so whn I haven't done anything to her. Like she dosent kno me. She she's ma gf friend but she keeps yapping. I was thinking of beating her up. Or break her car windows or slash her tires. It's been almost 9 months that I had to keep shut. I'm tired of it. At first I did it cause of respect to ma gf. I ignored it a lot of times. And now I'm hearing a lot of S*** bout me. I'm really pissed. It's not only her it's her gf too n on top of that there us 3 more girls. To remind u they are or were my gf friends. she said to thm stuuf and thy stop but now thy doing it again. Not only dat but before I do something to thm I need an advice. Gf said to ignore thm. I told her dat I'm tired if this crap. I gave to put her n thm in there place...... ADVICE