That calculation of the ship is kinda weird, especially since in other ocasions, Samus' ship wasn't shown to be that quick or speed wasn't clear, like Zero Mission, where in a chase and at full speed ( or we can assume it was full speed ) it reached the Planet's orbit in a cutscene of time and then was shotdown. If we are to say her ship is 10,000,000 FTL, then I'd gladly do a calculation of Samus leaving Ceres ( which for all we know could actually be exactly where Ceres, the dwarf planet, is ), passing through the asteroid belt and coming back. I'm pretty sure if I were to do that, then she would still be FTL but with a more reliable calculation. Also, we don't know how long it took from Samus to Tetra, so for all we know, it could have taken months and months of journey and the calc mentions it being almost instantaneous.
So, even if we consider that calculation, that would imply Samus without a ship is quicker than her ship, which is absolutely crazy. I mean, she can basically fly with the Space Jump, if she was that quick she could just fly away and leave her ship, unless she can't breathe in space due to her suit not having oxygen. It's base is also speculation ( Metroid Prime: Hunters ) since that game is almost non-canon ( the only thing that could possibly tie it with the series is Sylux's ship chasing Samus at the end of Prime 3(?) and even then, it's not confirmed to be Sylux in any other game ).
Also, isn't the mentioned Ridly META-Ridley? If so, he is shown to be QUICKER than Samus, so it makes complete sense. In fact, if it is MetaRidley, he is above Samus in speed and possibly in AP, since his defeat was caused due to weakness in his armor, not for being inferior to Samus in stats. This is stated in the wiki page of MetaRidley and in Metroid Prime. And Omega Ridley is superior Meta Ridley in basically everything but speed, which is the reason he is defeated.