Of course this is my narrow opinion. Someone in very early sobriety who is still struggling has a beer. It is a slip in my book. They realized the err in their ways, put it behind them and continue through their journey to attain sobriety.
For someone with some sober time to pick up a drink - and continue to drink is only MY definition of a relapse. Semantics or whatever. If you get out of the pool and are not yet finished drying off... To me a relapse means going full tilt drinking again. But that's just me. Anyway, it's Christmas. Let's not put too much emphasis on it. Someone made a mistake in their mind. They corrected it and moved forward - that is the important thing after all, isn't it?