I'm going to write a novel.
Nejire is 2.38x stronger and more durable than Lucy. Meaning most of Lucy's attacks can be easily overpowered with Wave Motion. Even if Leo's light attacks are faster, she can easily tank them without major damage, or block with Wave Motion. This holds true for all of Lucy's spirit attacks as well.
Taurus might as well be worthless, he lacks range, flight, and is vastly inferior to Nejire. Cancer and Capricorn, are just as bad as Taurus.
Sagittarius has useful ranged attacks, but once again they're going to be vastly inferior to Nejire. They're a bit slower as well, making them easy to dodge or block. Aries and Scorpio fall under this category as well. They're ranged attacks aren't going to be useful in this fight. Nejire can avoid, block, or blow away any of their attacks.
Virgo's ranged attacks aren't as useful as Sagittarius, as Nejire's superior LS means she can escape from any rock restraints. While digging underground is good mobility for both Virgo and Lucy to avoid attacks, since Nejire will be flying in the air they cannot do anything more than hide from her.
Leo has the most useful ranged attacks as they move at the Speed of Light, but as explained they're easily blocked. Even those that hit won't do much damage as they're 2.38x weaker than her durability. Lion's Brilliance would be his most useful spell, as he can temporary blind Nejire, which could leave her open to attack.
Now moving onto Gemini. First off, it's rare for Lucy to have Gemini turn into her opponent. Even against Mimi she never did that and Mimi is inferior to Nejire, so I say it's out of character to begin with. However, Gemini cannot transform into someone unless they touch the person at some point. Gemini cannot turn into Nejire unless they touch her, which is impossible. Nejire is going to be flying in the air and will not let herself be touched by Gemini. As long as she keeps her distance, she's safe.
Everything said applies to Lucy's Star Dress as well. Aquarius form doesn't add anything new either. She's still 2.38x weaker than Nejire and has vastly inferior LS as well. Gemini form hasn't shown much of anything, but she still cannot transform into Nejire without touching her.
Star Dress Mix. This is something that takes a lot out of Lucy and needs to used in short burst. So she isn't using more than one attack before turning back to normal.
Aquarius x Scorpio wouldn't be that good, as the attack can be avoided by Nejire. Same with Leo x Virgo, since the attack comes from the ground and Nejire is flying.
Aquarius x Gemini is the most dangerous as it can distract Nejire long enough for her to use Urano Metria. However, this is also the most draining of her Star Dress forms. With it only being an unknown amount higher than 53.22 Petatons, Nejire can survive this with normal damage. Her water clones are also not 53.22 Petatons, as Kiria was easily able to slice them apart with her normal attacks. They're only distractions for Lucy, not for damaging her opponent.
It's over 1.25x stronger than Nejire's durability, certainty not enough to inflict fatal damage. Nejire also has very good stamina as well, being able to fight for over 20 minutes against an opponent that was constantly absorbing her own vitality. She can without a doubt outlast Lucy in this battle.
I highly doubt Lucy can even use Urano Metria more than twice without dropping from her lose of stamina. Assuming she can use it twice to begin with.
Lucy's ranged attacks can be avoided, blocked, or just withstand if they hit her. While Nejire's must be avoided at all cost, as they'll blow away any of Lucy's attacks. Horologium's protection can only be used once during battle, so it's not an absolute defense, and it's only activated when Lucy is in severe danger.
Lucy's going to be burning through her stamina while Nejire can keep going. With her superior LS she can easily restrain Lucy, which she has no way out of besides Horologium's protection. However, Nejire isn't blood thirsty and isn't going to kill Lucy. She'll want to incapacitate her instead, as she is a hero.
If she grabs Lucy and flies up, there isn't much Lucy can do to prevent Nejire from knocking her out.
Being knocked out doesn't even summon Horologium, as shown when Mimi defeats Lucy, so it's possible he doesn't even show up here.
Nejire has superior AP/Dura, stamina, Lifting Strength, and mobility with her flight. While Lucy can inflict real damage with Star Dress Mix and Urano Metria. Nejire can defend against the former, and survive the latter. However, I doubt she'd let Lucy use it twice, even if she isn't already tired from using Star Dress Mix + Urano Metria.
Also, even if Nejire's Wave Motion cannot stop Star Dress Mix attacks or Urano Metria. She can cushion the blow by shielding herself with Wave Motion.
Lucy does has superior variety of attacks, numbers, and can surpass Nejire's AP with certain attacks. But her inferior stamina means she's more likely to run out of steam before putting Nejire down. And getting grabbed by Nejire's Wave Motion would basically end the fight. I'd assumed Lucy could use Water Body as well, but she has not been shown to do that. Meaning she has no real way of escaping Nejire's Wave Motion.
I'll be voting for Nejire myself.
