Is this not a tad out of proportion? She says 'one of u...the other would be messed up!' presumably meaning 'I wouldn't ding-dang-dong my sister'.
That's what the above tweets reads like to me.
I understand where you're coming from, but there was no reason for Edele to say "messed up" if she didn't want to bang Keavy. It just insinuates strongly that she would almost certainly go there if Keavy wasn't her sister. If Edele didn't want to shag Keavy, she should've stopped after "well one of you anyway".