Someone that needs you to validate their beliefs and therefore their own existence has a very low self esteem. Nothing you like or share on Facebook is going to change that.
In fact the more you do it and allow her to emotionally blackmail you the longer she will continue to " share" this stuff with you.
Set some boundaries in this and all your friendships.
Some people may not like them and may push those boundaries but if they refuse to accept them it shows you that they do not respect you.
Without respect from them this sounds like a one sided relationship. Shalom