That's a good question!
The sections I believe would be applicable are in the "General" and "Structural" disqualification sections of the SOP, though there is not any verbiage specifically addressing drooping ear tips. Due to copyright restrictions I can't reproduce the whole text here, but hopefully you have an ARBA
Standard of Perfection you can refer to.
p. 35,
General "...Any deviation from the normally accepted condition of body structure..."
and
p. 36,
Structural - Ears "...torn ears or ears with a portion missing, must noticeably detract from the general appearance..."
Poor ear carriage is generally a fault, not a DQ, though it does depend on the specific breed and the degree of deviation from the ideal. In this case, I think it would come down to each judge's discretion as to whether it is a defect that noticeably detracts from the rabbit's appearance.
She probably won't be in the running for Best in Show, but I'd enter her in her breed classes and see what the judges have to say. They may have some valuable insight into the situation from their years of experience handling all sorts of rabbits. Did the former owner have any information about how the rabbit did in her previous show(s)?
I've seen drooping ear tips in cases of extreme heat, or due to a vitamin E deficiency, or due to injury to the ear or to the nervous system. It's hard to be sure what I'm looking at in these photos but because it's only one ear, and because it looks like a distinct crease rather than a soft droop, I'd be inclined to think it was some sort of injury.