Lady of Quality

I find it interesting that I read this one very shortly after Black Sheep, since they have some noticeably similiarities in characters. Both books have an older (than 25) spinster who is trying to help a younger girl (niece or random stranger) with a marriage problem (one is in love with an inappropriate fortune-hunter, one not in love with her family's choice for husband). Both books have a gentleman guardian of the younger girl who shows less interest in being a guardian than the spinster believes he ought to, and who has a somewhat scandalous past and behaves outrageously & rudely (according to the strict dictates of society). The endings, however, were different and amusing in different ways (Black Sheep being the more unusual).