I know that Daisy has annoyed a LOT of people and I can totally see why. But I still sympathise with her. Remember that she grew up in a very large and very poor family. She didn't have people to look after her and let her know she wa loved. And she has been stuck in the kitchen at Downton for a very young age, surrounded by people who still see her as a child. See Mrs Hughe comment, callingg her one of the 'young ones'. She hasn't grown up because she nevr had an oppurtunity to do so. She went to school until she was eleven, never lived on her own and never gained independance. That's why I am sorry that she didn't move to London in the end. Not only that, she has just realised that there is a very firm hierarchy in place and she is very close to the bottom. So I can see why she is angry and occaisonally treats others who are trying to help her unfairly, becaue it has just sunk into her that her entire life has been unfair. Wouldn't you be angry, knowing that you are probably the least important person you know? And to give her credit, she is really trying to escape the situation she's in.
And as for her jealousy regarding Mr Mason and Mrs Patmore, these two are probably the first people she had a genuine connection with. They are her only parental figures and as she grew up in a household full of people and left when she was eleven, I can see how losing the love and stability those bring her would be awful for her and why Daisy is frightened of them leaving her. Yes, she is behaving in an immature fashion and she isn't being rational, but she is only really beginning to have a chance to mature. Like I said, she's been stuck in the kitchen for most of her life and is only really starting to acknowledge the world around. She isn't behaving like a rational adult yet, but she never had a chance to learn to become one.
My admiration comes from the effort she is putting into improving her lot in life and trying to better herself, instead of just accepting it as the status quo.