President's Privilege pairs well with Aru's hyper since it will lessen the cost by 20 stars, and it removes another card from Aru's hand to allow her to gain another 10 stars.
Rbits works as a way to buff Aru's bad DEF stat, which can allow her to survive things like Boss panels. It also wont be used against her much since she poses very little danger to her opponent since she has -1 ATK.
Since Aru has 2 EVD, Rainbow-Colored Circle pairs incredibly well with her since it will bring her to a whopping 4 EVD which will evade most attackers barring horrible luck, or ATK stats higher than 2.
Stat debuff cards like Reverse Attribute Field and Serious Battle are good on Aru since she has negative ATK and DEF, so they can allow her to make offensive plays, or to guarantee survival against massive threats.
Shield, Tactical Retreat, and Shield Counter provide crucial defensive utility for Aru since she falters against most aggressive plays. She also gets more use out of them than most characters since most fights she will be involved in will have her be defending since there is very little reason for her to fight players.
Characters with positive ATK stats such as Marc or Tomomo can easily KO Aru while she poses almost no threat to them.
Mimic can allow characters with subpar hypers to copy Aru's hyper and allow gain massive stars for themselves.
Since Aru is prone to getting KO'd in one hit, Gentleman's Battle works surprising well against her
Cards that boost ATK like I'm on Fire! or Big Magnum can allow characters that would otherwise have a hard time KOing Aru to easily KO her, or characters with positive ATK to near guarantee the KO.
Final Battle tends to be an easy way to KO Aru as she poses almost no risk to attackers, and her great EVD stat tends to falter with repeated combat
Traps that discard cards such as Flamethrower and Present Thief can remove Aru's cards, which puts her in an incredibly bad situation. However, these cards can also potentially help her as well if someone else lands on it, allowing her to give more cards with her hyper
Gift Exchange and Scrambled Eve put Aru in a really bad spot since it can remove the cards that Aru wants, and unlike the traps, Aru has almost no way of actually defending herself against them.
Play of the Gods can pull either Gift Exchange, Scrambled Eve, or Aru's hyper since her hyper is also an event.