Friends who bring you down
There is a difference between friends who criticize to help you and friends who criticize to hurt you.
If a friend tells you an offit doesen't look good on you she is trying to help you. If a friend is telling you that; "You'r ugly," "No guys like you," "You will be alone forever," "You can't get the job you want," then that person is not a friend. That person is trying to bring you down.
A true friend never makes you feel less than you should. They stick by your side no matter what you are going through and encourage you to go after what you want. They shouldn't be telling you things that will hurt you.
If you have a friend like that talk to her and if she doesen't change then lost that friend. It will only hinder you and down the line you will suffer from low self esteem. Be your own best friend, have confidence in yourself and know that you deserve to be treated with respect and not be around people who hurt you. Then the right friend will come along.