Ok, let me set the scene. Bea finds out she is going to be on BB. She knows Freddie is the Fav and once she is in the house she immediately makes friends with Freddie and they become very close. Now some of us who saw right through Bea early (while others thought she was a good person refusing to take part in the secret mission in favour of all people Freedie!) thought she was sucking up to the favourite to gain favour with the public so she cold ride his coat tails to the end and maybe finish 2nd or 3rd but.....she was actually playing a bigger and more complex game to take out Freddie!
Her plan was actually to get Freddit to like her or even fall in for her and lower his guard and feel comfortable with her. Now Freddie didnt help himself as he played into her hands and her plans by falling for Bea and started to get emotional and this made him lose focus and also his personality changed as he suddenly became Bea's lapdog who would defend her right or wrong (mostly wrong) when she was having arguments with others in the house.
Now once Bea had gained Freddie's confidence she suddenly turned on him which came as a shock with constant verbal attacks and tantrums and he completely lost it and just couldnt cope and started crying in bed and in the diary room and not been able to stand up to Bea and ultimately tarnished his image in the house and with the public. Maybe the damage was done already by all the bullying he had to put up with from Lisa's gang early in the show so he wasn't strong enough emotionally to stand up to Bea in the right manner so she brought out the worst in him or maybe she brought out the true Freddie but he just couldnt cope and just crumbled.
Marcus on the other hand stood up to Bea and kept his emotions in check and was able to show himself to be strong and sensible and i think the public saw that and he gained points which ultimately helped him to stay in the house.
So in the end Bea must be stoked to have just engineered the exit of the outright favourite by first gaining his confidence, getting him to lower his guard and then she stuck the knife in and now he's out.
Thats my theory anyway and she exibits all the chracteristics of a sociopath (see
http://www.mcafee.cc/Bin/sb.html) so really Freddie is prob better off mentally out of that house. Got to say that while i really hate Bea got to respect her game play a little. She would do great on the US version of BB and even Survivor.