You’ll need a good dose of luck on this one for sure!She’ll probably lie to you and say that it’s not a problem or bla bla bla,but when meth and coke is involved a lot it is a problem no matter what. I should know these things,I was addicted to H from I was 14 to 28,now Im 7 years clean(mostly clean,Im on methadone and Im on it for the rest of my life,but that won’t be too long because of complicated shit caused by my addiction)SO this talk you gonna have with your gf may save her life.If she keep up the lies and doesn’t admit to having a problem(if it wasn’t a problem she wouldn’t be lieing in the first place),you should honestly just leave her be and leave her ass because it is a very big chance that you’ll get dragged down with her even if you don’t think so right now.Please take care of yourself!