Here is a great link:
http://www2.scholastic.com/browse/article.jsp?id=10132
Well 2 years old is naturally a hard age... and at this age they do NOT even have full development of emotions, nor the capacity to handle what they are feeling.
But, at least your daughter IS expressing herself... although not pleasant.... but you must encourage it, otherwise she will withdraw and that will be worse. A child has to be able to communicate and express themselves and wallow in it even... so that they can explore and learn from it.
Think of yourself as a "Coach"... and "enabling" her to feel good about things and to know what certain "feelings" are, good or bad.
She needs to know that you are there for her no matter what, good OR bad. A child this age can also be "testing" for that and wanting to know about Mommy's "love" for them and loyalty etc. Do NOT take it personally when she says things that are hard to palate. For me, I would literally ALWAYS tell my daughter (after her brother was born), that I LOVE HER ALWAYS... no matter what, even when "Mommy" was grumpy or busy... that SHE is my FIRST "baby" and she always will be... and is special in my heart.... that even if I am busy, I think of her always and LOVE to see her smile...."
A child this age also begins to "compare" things in relation to themselves. Its NORMAL developmental based things. But you need to gauge her and guide her... not "reacting" to her acting-out.... but rather, guiding her.
The Book "How To Talk So Kids Will Listen, and Listen So Kids Will Talk" and, "Your 2 Year Old" are GREAT books. I really recommend them. You can get it at any bookstore or on www.amazon.com
You cannot "stop" jealousy with a snap of a finger... but rather, it is something that will be realized and managed better, in the child....with you "coaching" her.
And, your daughter was an "only child" all this time... NOW she is an "eldest child" and HER role in the family has changed. A child this age does not always know how to handle that. Adjustment to a baby, will take time.
Important also, is that the "eldest" child is still regarded in an age-appropriate way... not "suddenly" expected to behave "older" than they are or to "be" more than they are capable of. Otherwise, a child WILL get "stressed" by that and all that is put onto their shoulders.
A child with a new sibling, has to be given MORE attention many times... and nurturing. Otherwise they will feel lost in the shuffle... they are NOT able to, at this young an age, to completely understand why Mommy is so busy with baby, now. For us, we always explained to our daughter about how a baby is and what they do or cannot do... and how SHE can "help" too.. .and that her little brother LOVES her but can't do what she can do... but we are ALL A FAMILY. Not just her being around. That she is IMPORTANT.
Your daughter is probably just upset that you are not available for her as much now... and you have a "baby." So she is upset about it. Its okay. Tell her that you "understand" her... and its okay. For me, I would ALWAYS spend extra time with my daughter... just her and me, and we'd talk story... this is how my daughter bonded with me and felt better about "me" and how she STILL FIT INTO THE FAMILY.
Make allowances for her, meaning, do not expect "perfection" in her... because she is adjusting to so much right now, and is obviously having a hard time. Her behavior is telling you that. Try not to take her remarks personally. She is only 2 years old. But KEEP TO A ROUTINE for HER... just as it was before baby came onto the scene. A child NEEDS that... very important. They need CONSISTENCY in their daily routine and activities. In a kids shoes... having their entire life "changed" because of baby IS irksome and upsetting... and they become just a satellite floating around busy-ness and baby. They don't feel good about that. Keep your daughter's OWN routines and activities... something that is JUST for her. As it was before baby. And, let her have her own special things, and 'teach' her how SHE can help with her baby brother too... fostering kinship and empathy.
Kids, no matter how tough they seem to be... are quite tenderhearted...
All the best,
Susan