The poetess is Christina Rossetti -- writing about the feeling her brother, Dante Gabriel Rossetti, had for his "muse and wife," Elizabeth (Lizzie) Siddal (1829-1862}.
"One face looks out from all his canvases,
One selfsame figure sits or walks or leans:
We found her hidden just behind those screens,
That mirror gave back all her loveliness.
A queen in opal or in ruby dress,
A nameless girl in freshest summer-greens,
A saint, an angel - every canvas means
The same one meaning, neither more nor less.
He feeds upon her face by day and night,
And she with true kind eyes looks back on him,
Fair as the moon and joyful as the light:
Not wan with waiting, not with sorrow dim;
Not as she is, but was when hope shone bright;
Not as she is, but as she fills his dream."
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Christina Rossetti, In an Artist's Studio (1856)Dante Rossetti is one of my favourite artists and poets. Here is some of the classic pre-Raphaelite works he is well known for.

Mary's Girlhood
This is that blessed Mary, pre-elect
God's Virgin. Gone is a great while, and she
Dwelt young in Nazareth of Galilee.
Unto God's will she brought devout respect,
Profound simplicity of intellect,
And supreme patience. From her mother's knee
Faithful and hopeful; wise in charity;
Strong in grave peace; in pity circumspect.
So held she through her girlhood; as it were
An angel-water'd lily, that near God
Grows and is quiet. Till, one dawn at home,
She woke in her white bed, and had no fear
At all,--yet wept till sunshine, and felt aw'd:
Because the fulness of the time was come.
Dante Gabriel Rossetti