Many novels in George Eliot's time had a tendency to romanticize marriage. In Daniel Deronda, however, we get a pretty diverse mix of examples of what marriage can look like. Marriage is one of the key tools through which women could assert their place in society in the nineteenth century, so it wasn't just the two people getting married who had interests at stake; often, the whole family was involved. The Arrowpoints totally flip out when Catherine decides to marry Klesmer out of love; they threaten to disinherit her. Gwendolen marries Grandcourt to save her family from financial ruin. Hans realizes that Mirah will never marry him because he's not Jewish. Marriage isn't just about hearts and flowers in this book; it also provides a reflection of the way society at large tends to work.
Daniel Deronda shows us how marriage is a trap for women.
As unfortunate as it might seem to the modern woman, Mrs. Davilow is right: in Daniel Deronda marriage is the only good option for women.