Where's Flips when you need them? Or Nezchan? They usually understand these "hidden meanings" stories. Because this one missed me. Maybe she didn't think her feelings were love because when you truly love someone, you want them to be happy, no matter who with. And she didn't want sempai's love to come true. Though she didn't realize that she herself is sempai's love. I dunno.
Well since you asked...
I don't think Maki was ever aware that she was Hirasaka's love. She was, of course, and continues to be the one Hirasaka looks at, and that's why Hirasaka puts the ring on her wrist.
However, when she sees that Maki has a ring with her (that was forced on her by her friend) she assumes Maki is in love with someone else. So she's heartbroken of course, but keeps looking at Maki. Maki misses all of this, and assumes that Hirasawa is in love with some guy or something. Later, she tries to symbolically break Hirasawa's love for this mystery person by cutting the ring, but realizes it's meaningless to do so. However, she cuts her own because she thinks that relying on the ring is coercive (but doesn't think it through that then Hirasawa's ring would be too) rather than honestly being in love.
It seems like Hirasawa somehow realizes that Maki removed her own ring at the end, rather than letting it break and thus having her love be realized, and thus she still has hope.
That's my take. It's definitely bittersweet, but at least it leaves a slender thread of possibility at the end.
Thank you very much.