Should I, shouldn't I?

Assalamu'alaikum

Hi guys! How is everyone? I hope no one is catching a cold due to the weather conditions lately. I am good here. Just recovering from cough, but am still having it though it is not as bad as last week :) 

So I have a friend, a new one actually. We were good at first and suddenly I don't know what happened, that person suddenly shows hatred towards me. Not directly though. Like for example, he/she will emails everyone in our group whenever he/she got something good, but not me. I don't know where did it all went wrong. Sometimes I felt like that person was just jealous of me, which I myself is still trying to figure out what is the one thing that I have, that he/she didn't. I am totally clueless ??? 

That person always asked for my help back in the days when we were good. I am glad to help, because we are friends, right? That is what friends should do to each other. And now, out of the blue, that person started to kick me out of his/her life. Started to ignore me whenever he/she feels like so, and talk to me whenever he/she feels like so. I am a little mad, of course; because I didn't like people used me like that. Being kind to me when he/she wanted to ask for a help from me. Friends share their laughs and sorrows together. Not just happy times. So when he/she decided to ignore me, I started wondering, should I do the same to him/her too? 

There are times when I am hurt with what he/she said, but then, as time passes by, I recovered and just let it go. Never would have crossed my mind to like totally ignore him/her. Because true friends just don't quit on each other :( So now, things has elevated to another stage. He/she will not even respond to me in our group. Whenever I ask a question, no respond. But when everyone else is talking, he/she would suddenly appear and continues chit chatting like nothing is wrong. I am sad, seriously. Because I didn't know what I did wrong and made me deserve this. I helped him/her a lot though but never have I asked for any help in return because that is my principal. I just don't like to ask for help. I am so sad because I never thought he/she could be this cruel.

I don't want to hate him/her, because we used to be good to each other. But I don't like the way he/she treated me now, too. What should I do? Should I just pretend like nothing is wrong? Should I just refrain myself from getting mad? Should I just continue to give him/her a helping hand whenever he/she ask for one? Of course deep down inside of me, the devil is suggesting just to get out of the group and forget about him/her. Forget that we have been friends before. Treat him/her back like what he/she did to me. But I can't do that. I am not the kind of person that simply just be mean to someone that I used to be good with. I am in a dilemma. I need opinions and advises. Please help me! :(

Love,

~Husna S