Having actually seen it this time, I think you have something there.

Sam Tyler and Gene Hunt drank almost continuously, but we very rarely saw them actually get drunk. So it does kind of come across as overemphasising the Delicacy of the Feminine Constitution. But also: There's the point that Alex is more convinced that nothing is real than Sam was, having studied his case. So there's a bit of 'none of this matters' to her attitude.