Why am I always let down!?

Yeah, that's a tough one to swallow.

Losing your unfaithful husband early on in your marriage, as painful as that may be, was actually a blessing even though I'm sure the betrayal was knife deep.

Then, your friend switches sides and is now with the enemy. Of course you are deeply hurt and betrayed. I would be as well.

It is time to let go and move on...but how do you do that?

You begin by forgiving yourself for choosing lousy people to be part of your life. You made some up-front mistakes and it's time to forgive yourself for trusting the wrong people.

Carry on by being the best you can be and by taking the time for people to EARN your trust and respect before giving more than you are prepared to lose.

You can do this!

I dont know. That situation has nothing to do with you.

We all can think of what may happen just by a little bit of information but really this is just what we speculate We may think maybe she was already friends but we maybe far from truth. If she was already friends then whom are you to judge who this person may speak too?  If this friend wasn’t friends already then this maybe upsetting but also at least you know what kind of people they really are! Leave all this negative energy and focus on yourself be glad that you are free from such nasty people, your time will come  when you look back and think im glad all this happened as they say things happen for a reason, Let your reason be happiness

Because your expectations are out of line with reality. You expected your husband to keep his wedding vows. You expected that you knew what kind of guy you were marrying. You expected people who were your friends to support you. You expected that they support would mean not being in contact with, let alone friends with, your ex or his new girlfriend.

So, you can choose to be grateful that you uncovered the "truth" about these people, wash your hands of them, and move on -- and or you can reevaluate your expectations to see if any of them are unrealistic. 

Many people try to maintain friendships with both people when a couple splits.  Some people choose "sides" based on whomever they like better or who they believe is "right." Most relationships end -- they run their course for whatever reason.  You can either continue to brood and feel betrayed or you can be grateful that the hearts of those people have been reveal and you are now free of them and free to move forward to better things.  

If you can't do that on your own, please consider getting counseling. However you feel is legitimate, but at some point, the only person you are hurting by holding onto those feeling is yourself. Your ex and your ex-school mate don't care.     

Presumably she was friends with that woman prior to their relationship?

Feel good that you see them for whoever they really are and thank God He's showing you ❤️.  Pray and give God the glory.  Good Luck and God Bless you.  They can't let you down if you aren't depending on them get a better support system you can depend on during good and bad times.

You like to play the victim, so you go out of your way to find "betrayal" in the innocent actions of other human beings. Your husband betrayed you. That's the only betrayal I see here. Your friend is just going on with her life, as should you.

You claim you're "always" let down yet only describe one occurrence of this. Maybe you're letting one incident, that even you admit is a little irrational, color your world view on everything else too. If you look for grief you can usually find it but if you look for happiness that's available too. 

I believe in Christ and God warned of persecution 

If you feel betrayed, you do.  Just move forward in your life and stop living in the past.  Live with presence.  It's the best thing you can do for yourself