Everyone saying she's "too forgiving", but in my eyes her decision to forgive Charlotte is a win-win for her. First, she gets a favor and the gratitude of the head maid, which is really valuable. And then there's Charlotte. She will either learn from her mistakes, or what's more likely, she'll do something stupid, waste this last chance, and get fired anyway. So the question is, will whatever stupid harrassment Charlotte comes up with be more costly than the benefit she can get from the head maid's favor? So long as Charlotte doesn't try to outright murder her, she'll come out ahead. And also, she gets to ask for compensation again.
Also, Charlotte shouldn't be insulting other people for being orphans when she lost her mother, and presumably father too. Else, why would the father send his daughter to live with his sister in law?