Wolves are among the few dangerous animals in Europe and may sometimes attack humans. Keeping them at bay means stopping them from coming too close to you.
These days, real wolves aren't such a problem, but metaphorical wolves are meant here. Metaphorical wolves would be things like hunger, poverty and homelessness. In the passage, she worked very hard in order to earn enough money to buy food and clothing and pay her rent -- not much money, but enough to keep her alive.