Sadly, as we can clearly see that this world is unjust and favour those with high rank skills, no matter how much of an ass they are (as long as they aren't outright criminals). So even if Elmina was to abuse her power, she would still be valued higher than the average Joes that she failed the exam on purpose because their low rank skills are deemed trash. And no, there's really no benefit to the guild, except for the sick enjoyment she gets out of failing people just for funsies.

I mean, given Elmina's personality, she still made it this far in life with connection to a powerful family for backing, it only confirms how rank determines all, enough for a certain family to exile a certain daughter and even plotted to have her killed.