How do you not be affected by negative people?

I have a friend that I used to enjoy being around, but as you get to know her you realize she is insecure, holds on to her past, makes every situation about her and loves to guilt trip. I tried explaining her behavior to her once and she got angry at me, even insulting me personally. She apologized the next day and became better – but she bounced back to her old ways in no time. I decided that trying to talk to her again would do nothing so I did not respond. I try to be polite when I see her or when she messages me, but I want to avoid her as much as possible. I imagine she must think I don’t care or am a jerk, but I don’t know what to do. She brings me down too much. Is there a better way to go about this? I constantly tried to help bring herself up but she has always wanted to stay down.

Second scenario… my co-worker has been exhaustiing me to no end. She LOVES to gossip, and in our job we have a lot of private information about our workers that we are not allowed to talk about. She will come up to me and say, “I read about ____! WOW!” and general talking about people as well. She is always negative, “I don’t want to do this or that” and I’ll ask “Why?” and she says, “Jsut cause…” etc. She complains if we have to stay late, she complains about everything and can find the bad in anything and complain about it. She will take tons of breaks and feel no guilt.

It drives me UP THE WALL! I’m not as confident as I used to be because these people have been bringing me down so bad. Too much negative energy. How do I get myself back and stay strong? I can’t get away from my co worker…