#ons chapter 56

Actually, Mahiru wanted Shinoa to gain confidence. (Of course that was asking something quite hard considering Shinoa pretry much had an adversion to the whole concept of falling in love. Like some anon said before, Shinoa's vision and insight towards emotions in general were on black and white: feel = possessed; don't feel = safe)

Let's recall that legendary panel:

At that time, Shinoa kept people at bay; she did treasure her teammates but not to the point of her allowing herself to feel; besides, at that point Shikama Doji was pretty much tied to Tenri Hiragi.

This is heavily visible until her confrontation with Shikama is inevitable (aka back in Ch. 74); she didn't really care about herself if she was cone forever considering she had low self steem

But, after she got rescued, after everything that happened; you could say she started to see that her emotions weren't exactly evil; it all depended on how she handled them in order to actually pull a fight against Shikama.

For example, back in Ch. 99, she admited she was in love, it was evident but she pushed away the idea until saw she didn't go insane, lost herself or the sort; rather, it was a human emotion, something all humans face at one point of their lives. If anything, thanks to that push, that gave her the courage to stand and fight against the very entity that pretty much screwed her life:

At that point, she thought love = reason to live; but due to the events of Ch. 115-120, and up to Ch. 133, she understood just because she was in love didn't mean it was all there to life; if anything, it was more. It was about that philosophical question "the meaning of life".

Of course, for her, Mitsu or any other loving her does not make difference because it's something defined, something certain. She didn't reach a point of giving herself value because due to the past and the LNs, no one expected anything from her, no one was interested in her, and so, she thought that her dying would upset no one.

However, now things are different. Thanks to that push, thanks to the fact she realized that even if she loved Yuu, and Yuu left, it wasn't the end of the world; if anything, it was just starting.

And thanks to knowing she has the support of her squad, that she can express her emotions, that she can be a normal girl, that she can rely on others, it's when she actually pulls the fight against Shikama.

Her resolution of course has been boosted further thanks to her squad's support but also thanks to Mahiru's words.

Mahiru knew Shinoa has been powerful; back when Shinoa was a kid, she had to do bad to guarantee Shinoa wouldn't be subjected to further experimentation; and she made sure Shinoa hardened her heart so Shikama couldn't toy with it. That's why when Shinoa turned 16, it was the time Shinoa had to face her own battle:

So that's pretty much it anon.