Your farm seems to be working properly. At the end of her work cycle, some milk should appear in the harvest box.
You can just train your other villagers to get to this level. Other comments say that manually-leveled villagers tend to be better, because they do not spend points in stun resistance (which you do not need unless you're fighting Takumi, and Takumi doesn't come in raids).
Either way, training Giant, Little and Nickel and a few other special people gives better results than training normal villagers. Little and Nickel, in particular, seems to have very high growth values, while Giant is better from the start, and gets even better with training.