I feel like that's the surface explanation, and the thing maybe Catra tells herself, but Catra's characterization in this show is one of the things keeping me invested and wanting more.
Catra is a pretty strong representation of a person raised in an abusive, unhealthy relationship with her parental figure, with a dependence on her adoptive sister and protector. The momentary incompetence that allows the heroes to win the day isn't just the writers going "oh fuck they still have to save the day somehow uhhh...uhhh...okay! Scorpia sucks at manual dexterity and drops the remote or some shit," at least, not always. Catra brings her insecurity to work for her, as well as her grudge against Adora, and those things combine to handicap her judgement in critical moments, something everyone else in the show seems very much aware of, at least in the Horde.
Glimmer and Bow seem to be the only ones who've fallen for Catra's femme fatale act. She really just wants to be scratched behinds the ears and told she's a good girl, but she'd probably rather drown than admit it, because she's been bit so many times she doesn't trust anyone anymore.