It's a bit interesting to think about, but the Strong Sphere in a metaphorical sense kind of represents a darker path Liko could've gone down if she hadn't met the right people who showed her where her real strength lies and told/showed her what she needed to hear/see.
Which is also part of why it was fitting that Liko was the one who got Dash to see the errors of her ways and stop using the Strong Sphere. Dash resorted to it as an act of desperation because she felt she needed tangible proof of strength to match her friends, since she failed her Tera Training and had to revoke the right to use a Tera Orb, while her friends passed and had Tera Orbs. Partially because Liko is someone who understands bonds well because her empathy and capacity for connection are her key strengths as a person, but also because of this. Liko almost failed her Tera Training, and Grusha was adamant about not giving her a second chance, and that deeply hurt her. Despite what she went through directly afterward, she was set on the right path, since she and Amethio talked it out and Amethio called her out on her defeatism, and then she ended up proving her worth when she faced Sidian and not only defeated him but won over his respect, which finally convinced Grusha against all odds. She proved him wrong even when he had already made up his mind about her.
I say that because Liko is actually quite vulnerable to the thief that compares, ie intense self-comparison, despite outwardly trying to act considerate of others. She was not only upset by her own failure to pass her Terastal Usage Test against Grusha, but was evidently feeling like she was being left behind by Roy and Dot, who had passed theirs. She froze when Amethio used Tera against her because it reminded her of what, in her mind, she was about to lose, and seeing him have that power-up too basically paralyzed her mentally. Talking it out with him got her out of her funk and helped both of them understand each other better, and that also tied into how Liko got Dash to realize the error of her ways much later. She told Dash to actually tell her friends Niko and Rob her feelings, and say it right there and then, because if she doesn't do it now, she'll regret it. That also ties into another theme of Horizons, which is talking things out, because the unwillingness to communicate leads to hurt. In Dash's case her telling Niko and Rob about her own insecurity since she felt left behind after failing the Tera Training finally set her on the right path because they not only understood but encouraged her, because they pointed out how good she was even without Tera, and also told her that there will always be a second chance to do Tera Training again which was another key point she had to realize. You don't have to declare yourself worthless from one setback, which is also something Amethio told Liko back then, also adding a nice continuity.
Liko despite her self-sacrificing tendencies can also be pretty intensely self-centered and envious at times, which she shows quite a bit both early in the show and at the beginning of the timeskip:
She tries to hide it, but underneath her tendency to push herself aside for others' happiness she can get pretty intense in wanting things for herself.
Her happiness for her friends is genuine but she also tends to hide how much she wants that same level of success and accomplishment for herself.
"What about me? What am I doing? I need to be the greatest like they are."
When you think about it that way she's actually the kind of person who, if things hadn't lined up nicely and she hadn't been around the right people, both friends and even adversaries, who showed her how she was very much moving forward and a strong Trainer in her own right, could've become ruthlessly fixated on trying to gain power for herself by any means necessary and going down a darker path of no return, especially after her loss to Grusha in the Terastal Debut arc. Fortunately, she did constantly meet the right people who got her to see what she needed to see each time, including her Meowscarada, and she thus never actually lost sight of what mattered or where her strengths are, chiefly her bonds and her friendships.
Because she's managed to have people who saved her from going down a path of relentless pursuit of power at the expense of what mattered, she herself was able to save someone who was actually on the way of walking down that path (Dash/Bocco) and get her off of that path before she could reach a point of no return, and remind her of what was truly important (her friends).
