i know what you mean, but, I can totally see Belles side.
She was hurt, how would you feel if the guy you loved 200% and who you thought loved you 200% was moving on so quick.
And, Aden did say in his letter that he wanted them to re-unite when she got out (I think he did)
Which is why Belle must have felt even more hurt. Also, she was messed up, drugs screw you over, so that is another main factor to why she reacted the way she did. Plus, Aden did all that with Nicole, whilst having NO emotional feelings towards her, like love for example. Whereas, Belle loved Aden & liked Angelo, and didnt want to hurt Angelo, but in her heart knw she loved Aden.
(: