Gamble! should mainly be used when Yuki is low so that she can use it to KO herself and be able to revive at full HP. The only other uses are to potentially remove Krilla's overheal, shut down Miusaki trying to use Solid Witch, or as a desperate way to KO someone in the lead to stall the game and give Yuki a potential chance of winning.
Mimic can be a very useful card as it can supply Yuki with stronger hyper cards from other players. Under the right circumstances, the card can make Yuki a much deadlier and unpredictable opponent.
Sink or Swim can allow Yuki to gain much more stars from a KO against a low HP target while the stat nerf doesn't matter as much since she will have 1 ATK for still reliable KO's. However, this card can also be used against her reliably when she is at 1 HP since she only has -1 EVD.
Desperate Modification is Yuki's best defensive card since it allows her to more reliably evade attacks that aren't a 5 or higher, which is massive whenever she is at 1 HP. It also serves an offensive purpose since it makes getting an 8 on attack happen half the time, so it ends up being a decent card for getting an unlikely KO if Yuki is in desperate need of one.
Final Battle can be really good for Yuki since the only characters she loses to on average if she goes first are Tequila, Store Manager, Sherry, and Islayif they are at full HP, so she can play it relatively safely for a KO that she desperately needs.
Gift Exchange and Scrambled Eve allow Yuki to easily disrupt card usage while not being affected by it as much since her amazing stat line makes her not reliant on cards.
Lucky Sevens fulfills multiple roles for Yuki. The main thing is that it gives Yuki more power on average, especially the chance to KO in one hit. This power increase allows Yuki to beat Sherry on average when they are both at full HP. She doesn't have to rely on having it herself to achieve the bonus power since she gets the same rolls on average against someone else holding Lucky Sevens. It also allows her to recover faster on average, but this isn't as important as it is on Tomomo. The 7 roll can also allow Yuki to reach a target that would have otherwise been impossible to reach.
Shield, Tactical Retreat, and Shield Counter can be effective against Yuki, as they can either reduce or prevent her from dealing damage. They also prevent her from using them aggressively for a safe fight since they must be used when defending. Shield Counter is the best one against her since it guarantees escaping from her, and it will deal 3 damage to her to either scare her off of fighting for a while, or KO her and force her to wait out her 5 REC. However, it is best to avoid using it when she is at 3 HP or lower if at all possible so that she doesn't revive at full HP while keeping all of her stars. However, Shield Counter and Tactical Retreat can also be really good on Yuki herself, since she can use them to avoid near certain death when at 1 HP.
Dinner can be used to prevent Yuki from KOing her target, or force her to heal everyone else when she wants to heal, which makes her 2 ATK less oppressive.
Out of combat damage cards like Long-Distance Shot and Cloud of Seagulls can be devastating to Yuki since she has -1 EVD, however, she can also use them to become a much scarier threat than she already is.
Oh My Friend can be brutal against Yuki, as it can stop her from gaining stars from encounter panels, and also makes it likely for her to die if she steps on a boss panel. It can also easily put a stop to her if she decided to go for wins norma.
Pet Snacks similarly makes it harder for Yuki to gain stars from encounter panels while increasing the chance that she takes a serious hit.
Play of the Gods can be used whenever someone is low for a chance for it to pull Gamble! from Yuki's hand and allow them to reset to full HP.