Angry may be too strong a word, but she is frustrated and annoyed by them all for the way they have treated Jane and the rest of the Bennet family. When Bingley's sisters first issue the invite to the Netherfield ball they speak only to Jane and in passing to Elizabeth, they ignore everyone else and appear very rude.
At the Netherfield Ball, Darcy is beginning to act like a gentlemen towards Elizabeth, but he is shy and quiet, and she is frustrated with him. By this time she has also just recently heard all of the negative stories about him from Wickham, and even though it is all a bunch of lies, she doesn't know that, and this knowledge prejudices her against anything good about Darcy and his improved behavior here.
After the ball she is very upset for Jane to learn, in a rather cold letter, that Bingley, Darcy and the sisters are all leaving town and will not be returning anytime soon. She is dismayed the Bingley would go from being so clearly in love with Jane to this cold-hearted man who would just leave her without a word. She hurts for Jane's broken heart. She knows that the Bingley sisters want him to marry Darcy's sister, but can't believe Bingley isn't enough of his own man to follow his heart.