Denial is only to common with addiction. Why would her GP tell her work? That doesn’t happen, it’s confidentiality unless she was going to be at risk to herself or harm others. GPs refer to drug services etc so they want to support and so if they told every employer noone would get clean. That is an excuse I agree.
Every other day or every day doesn’t matter. If she uses a substance to chill out, relax or blot out stuff then it’s problematic because it implies she can’t do all those things in a healthy way.