Agatha feels she has to run away to avoid marriage because she doesn't have a choice. She is not allowed to choose who she marries. This shows that in Ancient Greek culture marriages were arranged for the women. They were not given a choice to marry for love. Also, this shows that marriage is something that is expected once a person reaches a certain age.
They saw a lot of Abandoned Horses.
The literary theme here is that women have a difficult time because nobody takes them seriously, or at least that's what it was like in the first half of the 20th century. Many people believed that women shouldn't be taken seriously and shouldn't have things like voting rights or rights to work or similar things because they were considered to be less serious than men, and that's putting it nicely because many people were not nice to them.