Angela was, in 1837, the wealthiest woman in England. You can read more about her at the above link, but you might like to know that in contrast to some heiresses today, she used her immense fortune toward charity, for the most part. She also, at an advanced age, "shocked polite society" by marrying her young secretary who was 40 years her junior.
The painting, done in the 1840s, shows her as a young woman in a beautiful gown (click on the picture to see larger). She kinda looks like Dolly Madison on the doughnut and cookies boxes (for those of you who remember the old advertisements).