Helen, you may be a student of painting, but you are a master of poetry! What an amazing haiku.
The opening line evokes art classes, which is a particularly vivid image for me because my own daughter has recently been attending an art school. The arrangement of objects for a "still life" painting is itself something of an art. Your unusual arrangement of lines into a 3-4-6 haiku seems deliberately to evoke the clumsiness of the beginning painter. It is "out of balance".
The skeleton is a very striking figure in the final line, and full of irony. It is, I believe, the key to this incredibly rich poem and contains layers of interpretation. Skeleton's in cupboards are secrets, and this poem rewards the searcher.
Usually "still life" paintings are of fruit or flowers. But of course even they are not "alive" at the time of painting. They are "skeletons" holding only the shape of the living object.
Another connotation of skeleton is the preliminary sketch the artist makes before painting the final work. One senses the art students diligently putting their "hearts into" that process.
But then the poet has used the specific and evocative phrase "pours her heart". Commonly we hear this in the context of "pouring your heart out" – refering to unburdening ourself, usually tearfully. Why should the artist be emotionally overwhelmed? I think the next word is the secret – "into". When I studied anatomy as a medical student, we were solemnly instructed to remember the skeletons we were using had each been a living person who had nobly donated their remains to the school. Is this the source of the poet's emotional turmoil? The realization of the life that had previously animated the skeletal limbs? She is responding by applying herself diligently to try and capture and honour that life.
And so she has – in words! She has clothed that bare skeleton with layer upon layer of life, thought and emotion – in a poem! This is truly a miraculous work that leaves me in awe.