M.P.
Sounds like she is feeling insecure as well as being a sensitive child. Find ways to give her positive attention and include her in daily activities during which she feels good about herself and is expressing happiness.
Talk with her about how she's feeling when she cries. Try talking both when she is crying and at a later time when she's relaxed and feeling good. You can read stories to her that will provide a basis for the talking.
I also recommend that you read or listen to the book "Talk so Your Kids Will Hear & Listen so Your Kids Will Talk by Faber and Maslish. How we word things makes a big difference in how others hear and interpret what we say. The book also helps us understand reasons behind what kids do and say.