Caroline in season 4 went on and on about the Stefan diet and how Elena should go on it but Caroline isn’t even on the Stefan diet. she drink from blood bags. what do tu think about this?

Caroline's a hypocrite. Best example: "Someone who does terrible things is just terrible"

Stefan has done terrible things (and so has Damon!Don't freak out on me, Stefan fans), and yet she's best friends with him.

I think that Caroline was just being a friend. In the beginning of season4 Elena couldn't keep anything down,she could just take from the vein because Damon told her to. Caroline drinks from Blood Bags, Elena Tried until Damon dicho it was okay, She was sired to Damon.

I guess she thought it will be good for Elena in ways it wasn't good for her... But she did help her after the diet proved to be not good.