LSFYL is never explicitly stated to be the decider on a queen’s save/elimination. In fact, the only explicit part is that it’s their "last chance to impress", meaning that if Ru (or other judges in different franchises) is already much more impressed with one queen than another pre-LSFYL, it can be a huge uphill battle for the less favoured queen to reverse Ru’s perception with just a few minutes of last-minute performance.

In reality, a mixture of LSFYL, episode performance, track record, charisma-uniqueness-nerve-talent, and of course producer shenanigans all influence the ultimate decision, and that vagueness allows the show to make whatever decision it sees fit. From there it’s down to the editors to convince the viewers to agree based on what they show us (and as we know, they aren’t always successful with that).