BPD involves a deep seated belief system of believing ones self to be ultimately bad - and projecting feelings around that belief system onto others.
imagine that you believe you are ugly - not just hard on yourself, but believe it the same as you believe the sky is blue. if i came along and tried to convince you otherwise, its going to sound off, and make you uncomfortable. it may even come off as insincere.
A week passed and I reached out asking why and she went on saying I hate her, I hated every minute of being with her during a panic attack she had.
she feels/felt like a burden, may have felt embarrassed, and she felt that way to the extreme, to the point of interpreting you as hating every minute of being with her during a panic attack.
we all do this to an extent. you walk into a room and feel self conscious, you imagine everyone is staring at you, and the negative things they might be thinking. you may or may not rationalize that its in your head. in this case (her case), you dont; feelings = fact.