Difference between meth and cocaine?

I am worried for my friend. She is 21 years old and already has several years of experience with drug use. Cocaine was the last thing she has been using; she told me that herself and now I think she is taking meth. I cannot say that for sure, our mutual friend told me that and I would like to know if that is true. How to see a difference between meth and cocaine?

The easiest way is through physical examination. Meth looks more like a salt, it is a crystal. Cocaine is a powder, I guess you already know that. To be certain, you could burn both coke and meth and see what happens. Meth burns clean and leaves no traces behind, while there are always some residuals after burning coke. If you really want to help her, then let her know that you are at her disposal, if she ever needs your help.