When we greet someone by any means and she does not even answer us then we must know that she has already answered us with her silence, no one is indispensable in anyone's life, neither we for anyone nor they for us, unless it is someone very close to us as some of our relatives and we have to see what has happened, maybe we did something without realizing that she does not like it.
Otherwise, if someone next to us does not value our effort to give our support, let's put it aside and move forward, we are not more than anyone else but not less, that is what my parents taught me and I try to transmit it to my three children, they are life lessons that we must give to our children.
I know many people who try to do the impossible to get someone to like them and that can be counterproductive, we have to let things happen by themselves and not pressure anyone to accept us in their circle of friendship, the best friendships are those that occur naturally without any pressure from either side, what we have to be clear is that if someone does not really value what you do for them do not waste time and even to the side before the disappointment is greater.