Some people are selfish, and takers. Some are non-selfish and givers.

The givers always without a doubt get hurt and the takers always without a doubt don't get it and don't care...

The elderly lady may very well be a neighbour whom has felt sorry for your sister as well and she will no doubt get hurt and taken and so it goes on.

Bipolar is also a decease and people aren't rational, so try not to take it all to heart.

Just keep being you, because a beautiful soul is exactly that, beautiful.

CW