Keerthija, first of all, nice post. Well put.
Now coming back to your question. You need to remember that this is a serial and that too a finite one and it is set in a fictional world. Here no one does anything for fun. Everything happens for a reason because they cannot afford to waste their precious episodes on frivolous things. Even if Mahir holds Bella's hand it will be for a reason. On the other hand the daily soaps have infinite number of episodes to waste so they can show n number of filler episodes. Jamini, Shaan, Vik, Vish were all out there to get Bella. Vik and Vish were the people she trusted the most and they betrayed her. Now Juhi is doing the same thing.
I am not saying what they show is fictional. In real life also there are chances that you will be betrayed by your best friend or your boyfriend will cheat on you. But we must remember that not everyone is out there to hurt you.
I firmly believe that Karma is a bitch and what goes around comes around. People say that you will have to suffer in your next life if you commit sins in this one. I beg to differ. Just like you can't leave a hotel without settling your account, you cannot leave this world without settling your account of good deeds v/s your bad deeds.
As Fibby said, you cannot stop trusting people just because someone betrayed you. Your trusting someone is your good karma and them betraying you is their bad karma. Just because you were betrayed by someone you don't set out to avenge that betrayal. Rest be assured that their life take care of them. They will pay for hurting you. Even if you don't get to see them suffer they will suffer.
Wanting to see someone suffer is a bad karma in itself. Never fall prey to that.
I know that is not very comforting but I have trick which i use. Look at it this way. Each person comes in your life for a specific purpose. If someone betrays you then think that maybe that person was in your life just to show what betrayal feels like and move on.
I believe in looking at things with an empowering context rather than one that makes you feel powerless.
So someone betraying you could be looked upon as
He/she taught me a life lesson instead of saying he/she betrayed me.
Learning means going ahead in life. Whereas betrayal is bitterness that makes you revisit those memories over and over again.
I hope I did not sound so preachy. I just thought that you are so young and innocent that maybe this little trick will help you in remaining innocent.