Yes, she is a strong character. She regularly hunted large murderous fauna with her bare hands for sustenance in the alternian wilderness. She beheaded an ogre with one swipe of her claws, and she tacklepounced her moirail Equius so hard they slid a distance in the sugar cube coated desert of her planet.
But she doesn’t get to do anything.
She is the silly catgirl shipper. Obsessed with roleplay and the romantic realtionships of her friends to a worrying degree. She survives alongside the rest of her friends to the end of the game, only to be denied entry into the universe they crated and stranded on a meteor in the far reaches of the game space. There, they futz around until she is ultimately murdered by Gamzee after attempting to avenge Equius, who Gamzee murdered right in front of her.
She gains a slight modicum of relevance when she is prototyped into Roxy’s kernlesprite alongside Feferi, creating Fefetasprite, to become Roxy’s guide. While we do not get to see any of it, Roxy states that she is quite the talker and they are friends. Her usefulness to the plot is only implied, and it is only when combined with another person that she gains this usefeulness. Things escalate however, when Erisol and ARquius argue, causing Fefeta to explode, and rendering Nepeta dead and irrelevant once again.
She remains this way until the retcon, where just before the final battle, Jasprose prototypes her into Jake’s empty kernelsprite, bringing her back to life just so she can hit on her. Because she is only a x1 prototyped sprite, when she shakes hands with Davesprite, they combine into Davepeta, much to the horror of Jasprose. With this newfound self-acceptance, Davepeta decides to help fight lord english, where they ultimately stab English in the back and fly into a black hole, presumably killing lord english and themself in the process.
A thing to note in her whole story, is the theme of being used for someone else’s gain. Aradia uses her to bring herself back into the corporeal world by being Nepeta’s client player. Gamzee uses her claws to score lines across his face as he breaks her arm in a vice grip, perhaps trying to metaphorically “divide himself into two” to help cement the misguided idea he as about being both of the Mirthful Messiahs. He then also uses her blood to sell to Jane ineffectively, and to Kanaya effectively, and also uses her decapitated head to create Fefetasprite for Roxy.
As Fefeta, she is used by Roxy to help aid her in her quest, and then she is further used by Erisol and ARquius to try and prove a point in an argument, during which she blows up. As a ghost she is used by Vriska to find the artifact that can kill lord english, and then Sollux uses her and Feferi to fly out of the cave they were in in a very funny gif. During the retcon timeline, she is used by Jasprose as a romantic rebound, since Kanaya is already dating the Rose from the retcon timeline.
She is finally used by the narrative itself to create Davepeta, who I love dearly but was honestly just there to get rid of davesprite and to have another kind of important character to fight lord english. Ultimately being used as a sort of deus ex machina to finish English off during the fight in the Epilogue, which is dubiously canon.