"...she did what she could in that way, by drawing houses and trees, hens and chickens, all very much like one another."

I wonder if this last part could mean that her drawing ability was so poor that one object was indistinguishable from another. Meaning her trees looked like chickens which looked like houses...without ever being able to tell which one was which. If so, the later comment on her drawing, "not enough even to attempt a sketch of her lover’s profile", would make perfect sense.