Quite the opposite of her younger sister, Monica is an assertive, straightforward and unpredictable young woman who tends to tell others what is on her mind, disregarding how others may take what she says. Unlike many other women of her upbringing and social status, she is rather masculine: she is skilled in horseback riding, while others usually sidesaddle; she walks around in a top hat and carries a cane and overall she is far from being a lady.

She is married to Frederick Mildrake - a clueless and naive man. She doesn't have feelings for him, but as she stated herself, Frederick was more passionate than the other admirers, which is why she decided to marry him. Nevertheless, despite her self-centered attitude she has a softer side as well, which she usually shows exclusively to her younger sister, whom she is fiercely protective of.

She started having a strong dislike for William after learning that he is a potential suitor for Eleanor. Monica believed that William is not the right person for Eleanor, because he wasn't able to value her more than Monica herself does. She also thought that William's ultimate desire was to profit from the marriage, and therefore - his behavior was shameless and insulting to Eleanor and the Campbell family.

After witnessing William's proposal to Eleanor she becomes distressed and decides to go on a trip to India. During the trip, Monica takes a liking in traditional clothing and accessories. Even after she comes home to England, she continues to wear a sari and various accessories such as bracelets, armlets and earrings. Her father insists that she should move out if she wants to continue walking around in such clothes. At that time it also becomes apparent that Monica has a particular aversion towards her father who openly has affairs with numerous women.