On VictorianLondon.Org there's a section devoted to wages for various occupations. Among those listed are washers (would that be the same as a laundress?), ironers, collar ironers, women matchbox maker's at home, women upholsters, seamstresses, tailoresses, female shop assistants, teachers, and female telegraph clerks. These references, however, are from later in the 19th century--from the late 1860s to the 1890s. Would employment opportunities have been largely the same in the 1840s? Was governessing or being a paid companion the best an impoverished single woman of the middle class could hope for, if she couldn't marry or had no desire to marry?
There is always more to say on a topic but you may be interested in this comment I wrote a couple of months ago on recent research into the Victorian businesswoman.