It's unfortunate that some human beings act this way. One thing I think about life and have learnt is not to expect anything from anyone, because I may just get disappointed or hurt. Some people are just there for what they will gain and they flee afterwards, but don't let it affect your kindness or restrain you from helping others. I know it may be difficult because it hurts to be treated that way.
There are acquaintances, friends, colleagues, strangers, all these people don't behave the same towards us. A friend will definitely stand by you through thick and thin.
We may be kind to people but that doesn't mean they are friends with us and vice versa.
I would say that, your friends will come, and you will experience true friendship. Be strong dear.
Thanks for sharing your experience.