Now we just need Arashi to have a crush on Mao and the triangle will be complete! (This would actually be my preferred pairing since I adore this type of dynamic)
The first panel here kind of implies that she does develop a crush on Mao, but it is a pretty understated reaction so your mileage may vary on the validity of this interpretation.
I hated Mao. Passionately. Exactly the type of pushy possessive asshole I can not stand. Also, is it my imagination, or is it kind of implied that Yuki's "unapproachable" reputation is the result of having a possessive freak such as Mao as her best friend?
On the one hand, Yuki is fairly sociable and outgoing with Arashi from the get-go, and also expresses her wish for Mao to have friends other than her (which would make it reasonable that she wants the same for herself, especially in light of how fast she befriended Arashi). On the other hand, she is perfectly aware that Mao does not want her to befriend other people, and Mao is very important to her. So my guess is that she keeps herself away from socialising with other people in order to placate Mao.
That would explain the apparent disconnect between Yuki's public image and how she acted with Arashi. There is also the fact that anyone who would potentially get close to Yuki would face the exact same vehement hatred and rudeness from Mao since basically the first second, and I imagine most people would immediately give up after that.
And even when Yuki invited Arashi to have lunch with them, she did it in part because she wanted Mao and Arashi to become friends, for Mao's benefit. All of which makes me believe that Yuki is entirely too mindful of Mao and is likely sacrificing her own social life in order to keep the nutjob happy.
I want a sequel.