I’ve read stuff like “Oh, why is Octavia being so mean to Lincoln about being a guard? He’s just trying to belong and to settle down and blah blah…“, but here’s what you need to understand.
Growing up, the guards were like her own personal boogieman. She grew
up terrified of them. The guards who used and raped her mother, who executed her mother and were going to execute her too (and yeah, I know not all guards were like that but enough guards were that it left a mark on young Octavia). She hates the Guard (and the Council too probably). And, now, the man she loves, a grounder, wants to be a guard? Nah, of course that doesn’t sit well with her.
Remember her reaction when she saw Bellamy in the uniform in 1x01?
And let’s not forget this precious gem:
As I said before, she hates them.
Besides, she’s never really belonged with the Sky People - not being allowed outside and never living with them, developing relationships, learning their ways, etc. All she knew of the Ark was what her family taught her. On the ground, she’s found the Grounders and she’s embraced their lifestyle, she’s earned their respect, she’s developed relationships.
The truth is, no matter how hard they try (and Octavia’s not even bothering to try because she knows this already), they’ll never fit in or be completely welcomed there. She just wants to leave with Lincoln, but there’s nowhere to go so she feels like she’s trapped again.
And let’s not forget PTSD. Just because she seems stronger than the others, it doesn’t mean she’s not hurting. She was already traumatized from how she was forced to grow up, then being locked up in solitary for a year with the guilt of being responsible for her mother’s death and now everything that’s happened on Earth. She’s messed up too.
